Water-treating agent and method for treating water

ABSTRACT

A water-treating agent comprising a ternary copolymer of conjugated dienesulfonic acid/(meth)acrylic acid/2-hydroxyethyl (meth)acrylate, or a ternary copolymer of conjugated dienesulfonic acid/(meth)acrylic acid/(meth)acrylamido-2-methylalkanesulfonic acid ternary copolymer, is effective against scaling and fouling in water systems and a method for treating water with the water-treating agent. When combined with a corrosion inhibitor, the water-treating agent exhibits an excellent anti corrosion effect.

BACKGROUND OF THE INVENTION

The present invention relates to a novel water-treating agent and a method for treating water with the novel water-treating agent. More precisely, the present invention relates to a novel water-treating agent which prevents scale, sludge, and slime deposition.

The novel water-treating agent of the present invention can be used in, for example, heating pipes, heat exchangers, condensers, reaction vessels, chemical reactors, and various pipe runs found in, for example, boilers, cooling water systems, hot water systems, chemical plants, and dust collecting water plants.

The novel water-treating agent of the present invention prevents such problems as heat transfer failure, flow rate reduction, and corrosion that are caused by the adhesion or deposition of scale, sludge, and slime onto heating pipes, heat exchangers, condensers, reactors for polymerization, and various other pipe lines.

The present invention also relates to a method of using the water-treating agent for treating water in, for example, heating pipes, heat exchangers, condensers, reaction vessels, chemical reactors, and various pipe runs found in, for example, boilers, cooling water systems, hot water systems, chemical plants, and dust collecting water plants.

Heretofore, polyphosphates and carboxylic acid polymers have been used as scale inhibiting and fouling prevention agents in boilers, cooling water systems, dust collecting water plants and water supply piping systems to prevent the adhesion of scale onto the surfaces of the metal parts kept in contact with water, to prevent the deposition of sludge onto such metal parts, and to prevent the local corrosion in the area under the fouled parts covered with scale and slime.

However, polyphosphates are inadequate in that they are easily hydrolyzed to give orthophosphates, which in turn precipitate as calcium phosphate in water systems having high pH and high calcium hardness at high temperatures. Hence, polyphosphates too often accelerate scale troubles instead of alleviating them.

In addition, waste waters containing phosphorus are problematic because the phosphorus laden waters cause eutrophication in closed water areas such as lakes, marshes and island seas. Hence, the use of phosphorus containing chemicals must be limited and are often regulated by law.

On the other hand, carboxylic acid polymers have their own problems. They form insoluble salts in water containing high concentrations of polyvalent metal ions, with the result that the polymers are not effective in such water. In particular, where the polymers are applied to water with a high calcium ion concentration, the water becomes cloudy due to the calcium salts forming and precipitating.

In Japanese Laid Open Patent Application No. 2-9496, a phosphorus free water-treating agent for scale inhibition is proposed which comprises a copolymer of a conjugated diene-sulfonic acid and (meth)acrylic acid which is said to be effective, even in systems having high metal ion concentrations, without being precipitated therein.

However, when compared with sodium polyacrylate, which has heretofore been used in conventional water-treating agents, the copolymer of 2-9496 is superior to sodium polyacrylate but is still not completely satisfactory. Therefore, a water-treating agent having much improved effectiveness against scale retarding and fouling is still needed.

OBJECTS AND SUMMARY OF THE INVENTION

It is an object of the present invention to provide a phosphorus-free water-treating agent which does not react with polyvalent ions to form insoluble salts.

It is an object of the present invention to provide a phosphorus-free water-treating agent which provides effective and long lasting inhibition of scale formation and a method for treating water therewith.

In addition, it is an object of the present invention to provide a water-treating agent having excellent metal corrosion prevention properties and a method for treating water therewith.

It is an object of the present invention to provide a phosphorus-free water-treating agent comprising a ternary copolymer comprising conjugated dienesulfonic acid units, (meth)acrylic acid units, and 2-hydroxyethyl (meth)acrylate units or (meth)acrylamido-2-methylalkanesulfonic acid units.

It is an object of the present invention to provide a ternary copolymer which exhibits excellent scaling inhibition and fouling prevention.

It is an object of the present invention to provide a water-treating agent comprising a ternary copolymer which is synthesized from:

A) a conjugated diene-sulfonic acid and/or its salt of the following general formula 1!: ##STR1## wherein R¹, R², R³, R⁴, R⁵ and R⁶ each represent a hydrogen atom, a methyl group or --SO₃ X¹, provided that one or more of R¹ to R⁶ are methyl groups, one or more of the remaining R¹ to R⁶ are groups of --SO₃ X¹, and wherein X¹ represents a hydrogen atom, a monovalent metal, an unsubstituted ammonium group, or an ammonium group mono substituted by an organic group;

B) a (meth)acrylic acid and/or its salts of the following general formula 2!: ##STR2## wherein R⁷ represents a hydrogen atom or a methyl group; and X² represents a hydrogen atom, a monovalent metal, an unsubstituted ammonium group, or an ammonium group mono-substituted by an organic group;

and C) a 2-hydroxyethyl (meth)acrylate of the following general formula 3!: ##STR3## wherein R⁸ represents either a hydrogen atom or a methyl group, or a (meth)acrylamido-2-methylalkanesulfonic acid and/or its salt of the following general formula 4!: ##STR4## wherein R⁹ and R¹⁰ each represent a hydrogen atom or a methyl group; and X³ represents a hydrogen atom, a monovalent metal, an unsubstituted ammonium group, or an ammonium group mono-substituted by an organic group.

It is an object of the present invention to provide a method for treating water, comprising adding to water systems a water-treating agent, in an amount of from 0.1 to 1000 mg/liter, that comprises a ternary copolymer synthesized from:

A) a conjugated diene-sulfonic acid and/or its salt of the following general formula 1!: ##STR5## wherein R¹, R², R³, R⁴, R⁵ and R⁶ each represent a hydrogen atom, a methyl group or --SO₃ X¹, provided that one or more of R¹ to R⁶ are methyl groups, one or more of the remaining R¹ to R⁶ are groups of --SO X¹ and wherein X¹ represents a hydrogen atom, a monovalent metal, an unsubstituted ammonium group, or an ammonium group mono substituted by an organic group;

B) a (meth)acrylic acid and/or its salts of the following general formula 2!: ##STR6## wherein R⁷ represents a hydrogen atom or a methyl group; and X² represents a hydrogen atom, a monovalent metal, an unsubstituted ammonium group, or an ammonium group mono substituted by an organic group;

and C) a 2-hydroxyethyl (meth)acrylate of the following general formula 3!: ##STR7## wherein R⁸ represents either a hydrogen atom or a methyl group, or a (meth)acrylamido-2-methylalkanesulfonic acid and/or its salt of the following general formula 4!: ##STR8##

wherein R⁹ and R¹⁰ each represent a hydrogen atom or a methyl group; and X³ represents a hydrogen atom, a monovalent metal, an unsubstituted ammonium group, or an ammonium group mono substituted by an organic group.

Briefly stated, a water-treating agent comprising a ternary copolymer of conjugated dienesulfonic acid/(meth)acrylic acid/2-hydroxyethyl (meth)acrylate, or a ternary copolymer of conjugated dienesulfonic acid/(meth)acrylic acid/(meth)acrylamido-2-methylalkanesulfonic acid ternary copolymer, is effective against scaling and fouling in water systems and a method for treating water with the water-treating agent. When combined with a corrosion inhibitor, the water-treating agent exhibits an excellent anti corrosion effect.

According to an embodiment of the present invention, a method to produce a water-treating agent comprises the step of:

polymerizing a combination comprising

A) a first monomer selected from the group consisting of a conjugated dienesulfonic acid and a salt of a conjugated dienesulfonic acid, the conjugated dienesulfonic acid represented by the general formula 1!: ##STR9## wherein R¹, R², R³, R⁴, R⁵ and R⁶ each represents a member selected from the group consisting of a hydrogen atom, a methyl substituent, and a --SO₃ X¹ substituent, wherein at least one of R¹ to R⁶ is a methyl substituent, wherein at least one of R¹ to R⁶ is a --SO₃ X¹ substituent, and wherein X¹ represents a member selected from the group consisting of hydrogen atom, a monovalent metal, an ammonium substituent, and an ammonium substituent which is mono substituted by an organic substituent;

B) a second monomer selected from the group consisting of a (meth)acrylic acid and a salt of a (meth)acrylic acid, the (meth)acrylic acid represented by the general formula 2!: ##STR10## wherein R⁷ represents a hydrogen atom or a methyl substituent; and X² represents a member selected from the group consisting of a hydrogen atom, a monovalent metal, an ammonium substituent, and an ammonium substituent which is mono substituted by an organic substituent;

and C) a third monomer selected from the group consisting of a 2-hydroxyethyl (meth)acrylate represented by the general formula 3!, a (meth)acrylamido-2-methylalkanesulfonic acid, and a salt of a (meth)acrylamido-2-methylalkanesulfonic acid, the (meth)acrylamido-2-methylalkanesulfonic acid represented by the general formula 4!: ##STR11## wherein R⁸ represents a hydrogen atom or a methyl substituent, ##STR12## wherein R⁹ and R¹⁰ are members selected from the group consisting of a hydrogen atom and a methyl substituent; and X³ represents a member selected from the group consisting of a hydrogen atom, a monovalent metal, an ammonium substituent, and an ammonium substituent which is mono substituted by an organic substituent,

to form a ternary copolymer.

According to another embodiment of the present invention, a method to produce a water-treating agent comprises mixing an isoprenesulfonic acid monomer, an acrylic acid monomer, and a 2-hydroxyethyl methacrylate monomer with water to produce an aqueous monomer solution, mixing the aqueous monomer solution with a polymerization initiator while heating and stirring a resultant mixture, maintaining an inert atmosphere over the resultant mixture, continuing heating and stirring until a desired polymerization is attained to produce an attained product, and partially neutralizing the attained product to produce a partially neutralized attained product.

According to an embodiment of the present invention, a method to produce a water-treating agent comprises mixing an isoprenesulfonic acid monomer, an acrylic acid monomer, and an acrylamido-2-methylpropanesulfonic acid monomer with water to produce an aqueous monomer solution, mixing the aqueous monomer solution with a polymerization initiator while heating and stirring a resultant mixture, maintaining an inert atmosphere over the resultant mixture, continuing heating and stirring until a desired polymerization is attained to produce an attained product, and partially neutralizing the attained product to produce a partially neutralized attained product.

According to an embodiment of the present invention, a method for treating water to prevent scale and slime formation and to prevent fouling, comprises the steps of:

polymerizing a combination comprising

A) a first monomer selected from the group consisting of a conjugated dienesulfonic acid and a salt of a conjugated dienesulfonic acid, the conjugated dienesulfonic acid represented by the general formula 1!: ##STR13## wherein R¹, R², R³, R⁴, R⁵ and R⁶ each represents a member selected from the group consisting of a hydrogen atom, a methyl substituent, and a --SO₃ X¹ substituent, wherein at least one of R¹ to R⁶ is a methyl substituent, wherein at least one of R¹ to R⁶ is a --SO₃ X¹ substituent, and wherein X¹ represents a member selected from the group consisting of hydrogen atom, a monovalent metal, an ammonium substituent, and an ammonium substituent which is mono substituted by an organic substituent;

B) a second monomer selected from the group consisting of a (meth)acrylic acid and a salt of a (meth)acrylic acid, the (meth)acrylic acid represented by the general formula 2!: ##STR14## wherein R⁷ represents a hydrogen atom or a methyl substituent; and X² represents a member selected from the group consisting of a hydrogen atom, a monovalent metal, an ammonium substituent, and an ammonium substituent which is mono substituted by an organic substituent;

and C) a third monomer selected from the group consisting of a 2-hydroxyethyl (meth)acrylate represented by the general formula 3!, a (meth)acrylamido-2-methylalkanesulfonic acid, and a salt of a (meth)acrylamido-2-methylalkanesulfonic acid, the (meth)acrylamido-2-methylalkanesulfonic acid represented by the general formula 4!: ##STR15## wherein R⁸ represents a hydrogen atom or a methyl substituent, ##STR16## wherein R⁹ and R^(l0) are members selected from the group consisting of a hydrogen atom and a methyl substituent; and X³ represents a member selected from the group consisting of a hydrogen atom, a monovalent metal, an ammonium substituent, and an ammonium substituent which is mono substituted by an organic substituent,

to form a ternary copolymer, and adding the ternary copolymer to a water system in an amount of from about 0.1 to about 1000 mg/liter.

According to another embodiment of the present invention, a water-treating agent for treating water to prevent scale and slime formation and to prevent fouling, comprises the product formed by polymerizing a combination comprising

A) a first monomer selected from the group consisting of a conjugated dienesulfonic acid and a salt of a conjugated dienesulfonic acid, the conjugated dienesulfonic acid represented by the general formula 1!: ##STR17## wherein R¹, R², R³, R⁴, R⁵ and R⁶ each represents a member selected from the group consisting of a hydrogen atom, a methyl substituent, and a --SO₃ X¹ substituent, wherein at least one of R¹ to R⁶ is a methyl substituent, wherein at least one of R¹ to R⁶ is a --SO₃ X¹ substituent, and wherein X¹ represents a member selected from the group consisting of hydrogen atom, a monovalent metal, an ammonium substituent, and an ammonium substituent which is mono substituted by an organic substituent;

B) a second monomer selected from the group consisting of a (meth)acrylic acid and a salt of a (meth)acrylic acid, the (meth)acrylic acid represented by the general formula 2!: ##STR18## wherein R⁷ represents a hydrogen atom or a methyl substituent; and X² represents a member selected from the group consisting of a hydrogen atom, a monovalent metal, an ammonium substituent, and an ammonium substituent which is mono substituted by an organic substituent;

and C) a third monomer selected from the group consisting of a 2-hydroxyethyl (meth)acrylate represented by the general formula 3!, a (meth)acrylamido-2-methylalkanesulfonic acid, and a salt of a (meth)acrylamido-2-methylalkanesulfonic acid, the (meth)acrylamido-2-methylalkanesulfonic acid represented by the general formula 4!: ##STR19## wherein R⁸ represents a hydrogen atom or a methyl substituent, ##STR20## wherein R⁹ and R¹⁰ are members selected from the group consisting of a hydrogen atom and a methyl substituent; and X³ represents a member selected from the group consisting of a hydrogen atom, a monovalent metal, an ammonium substituent, and an ammonium substituent which is mono substituted by an organic substituent,

to form a ternary copolymer.

According to another embodiment of the present invention, the ternary copolymer used as a water-treating agent comprises from about 5 to about 50 mol % of the unit derived from the conjugated dienesulfonic acid and/or its salt, from about 40 to about 90 mol % of the unit derived from the (moth)acrylic acid and/or its salt, and from about 1 to about 20 mol % of the unit derived from the (meth)acrylamido-2-methylalkanesulfonic acid and/or its salt.

According to still another embodiment of the present invention, the ternary copolymer used as a water-treating agent has a weight average molecular weight of from about 500 to about 300,000.

According to another embodiment of the present invention, the water-treating agent further includes a corrosion inhibitor and a ternary copolymer.

According to another embodiment of the present invention, the water-treating agent further includes a metal corrosion inhibitor and a ternary copolymer.

According to an embodiment of the present invention, the corrosion inhibitor to be optionally in the water-treating agent comprises at least one member selected from the group consisting of polyvalent metal salts, polyvalent metal phosphonates, polyvalent metal azoles, polyvalent metal phosphates, polyvalent metal phosphocarboxylates, polyvalent metal amines and polyvalent metal phosphoric esters.

According to an embodiment of the present invention, a method for treating water comprises adding to water systems a water-treating agent which comprises the ternary copolymer that includes from about 5 to about 50 mol % of the unit derived from the conjugated dienesulfonic acid and/or its salt, from about 40 to about 90 mol % of the unit derived from the (meth)acrylic acid and/or its salt, and from about 1 to about 20 mol % of the unit derived from the 2-hydroxyethyl (meth)acrylate.

According to another embodiment of the present invention, a method for treating water comprises adding to water systems a water-treating agent which comprises from about 5 to about 50 mol % of the unit derived from the conjugated dienesulfonic acid and/or its salt, from about 40 to about 90 mol % of the unit derived from the (meth)acrylic acid and/or its salt, and from about 1 to about 20 mol % of the unit derived from the (meth)acrylamido-2-methylalkanesulfonic acid and/or its salt.

According to still another embodiment of the present invention, a method for treating water comprises adding to water systems a water-treating agent which comprises the ternary copolymer having a weight-average molecular weight of from about 500 to about 300,000.

According to still another embodiment of the present invention, a method for treating water comprises adding to water systems a water-treating agent comprising a corrosion inhibitor in addition to a ternary copolymer.

According to still another embodiment of the present invention, a method for treating water comprises adding to water systems a water-treating agent comprising, in addition to a ternary copolymer, a corrosion inhibitor which includes at least one member selected from the group consisting of polyvalent metal salts, polyvalent metal phosphonates, polyvalent metal azoles, polyvalent metal phosphates, polyvalent metal phosphocarboxylates, polyvalent metal amines and polyvalent metal phosphoric esters.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow diagram of the pilot plant of a water-cooling system as used here in Examples 19 to 21 and Comparative Examples 41 to 42.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The water-treating agent of the present invention comprises a copolymer which is synthesized from the following three parts:

(A) a conjugated dienesulfonic acid and/or its salts of the following general formula 1!;

(B) a (meth)acrylic acid and/or its salts of the following general formula 2!; and

(C) a 2-hydroxyethyl (meth)acrylate of the following general formula 3! or a (meth)acrylamido-2-methylalkanesulfonic acid and/or its salt of the following general formula 4!: ##STR21##

In formula 1!, R¹, R², R³, R⁴, R⁵ and R⁶ each represents a hydrogen atom, a methyl group or the --SO₃ X¹ group, provided that one or more of R¹ to R⁶ are methyl groups, one or more of the remaining R¹ to R⁶ are --SO₃ X¹ groups, and in which X¹ represents a hydrogen atom, a monovalent metal, or an ammonium group. The ammonium group is either unsubstituted or mono substituted by an organic group.

In formula 2!, R⁷ represents a hydrogen atom or a methyl group; and X² represents a hydrogen atom, a monovalent metal, an unsubstituted ammonium group or an ammonium group mono substituted by an organic group.

In formula 3!, R⁸ represents a hydrogen atom or a methyl group.

In formula 4!, R⁹ and R¹⁰ each represent a hydrogen atom or a methyl group; and X³ represents a hydrogen atom, a monovalent metal, or an unsubstituted ammonium group or an ammonium group mono-substituted by an organic group.

In the above formulas, the ammonium group mono substituted by an organic group is, for example, an ammonium group formed through the reaction of --SO₃ H or --COOH with a primary amine. The primary amine includes, for example, methylamine, ethylamine, propylamine, isopropylamine, butylamine, isobutylamine, sec-butylamine, tert-butylamine, pentylamine, hexylamine, cyclohexylamine, benzylamine, and monoethanolamine.

In the water-treating agent of the present invention which has the ability to inhibit scaling and to prevent fouling in water plants, X¹ and X² each are preferably an alkali metal, more preferably sodium.

The conjugated dienesulfonic acid of formula 1! includes, for example, 2-methyl-1,3-butadiene-1-sulfonic acid, 2-methyl-1,3-butadiene-3-sulfonic acid, 2-methyl-1,3-butadiene-4-sulfonic acid, 1,3-pentadiene-1-sulfonic acid, 1,3-pentadiene-2-sulfonic acid, 1,3-pentadiene-3-sulfonic acid, 1,3-pentadiene-4-sulfonic acid, 2,3-dimethylbutadiene-1-sulfonic acid, 2-methyl-1,3-pentadiene-4-sulfonic acid, 3-methyl-1,3-pentadiene-1-sulfonic acid, 2-methyl-1,3-butadiene-1,3-disulfonic acid, and 2-methyl-1,3-butadiene-1,4-disulfonic acid.

The (meth)acrylic acid of formula 2! includes acrylic acid and methacrylic acid. Acrylic acid is preferably used in the water-treating agent of the present invention.

The 2-hydroxyethyl (meth)acrylate of formula 3! includes 2-hydroxyethyl acrylate and 2-hydroxyethyl methacrylate. 2-Hydroxyethyl methacrylate is preferably used in the water-treating agent of the present invention.

The method of producing the terpolymer of the present invention may be by any convenient conventional method. Copolymerizing the constituents including the conjugated dienesulfonic acid and/or its salt of formula 1!, the (meth)acrylic acid and/or its salt of formula 2!, and the 2-hydroxymethyl (meth)acrylate of formula 3! or the (meth)acrylamido-2-methylalkanesulfonic acid and/or its salt of formula 4! to obtain the ternary copolymer for use in the present invention is not specifically defined but may be by any convenient conventional method.

The monomer of formula 1!, the monomer of formula 2! and the monomer of formula 3! or 4! are all generally substantially soluble in water, and the ternary copolymer to be obtained through copolymerization of such monomers is also substantially soluble in water. Accordingly, a solution polymerization method using water as the medium is preferably employed to copolymerize the starting monomers for the present invention.

One example of solution polymerization using water as the medium, which is employable in the present invention, includes the steps of dissolving the pre-determined monomers in water, substituting the atmosphere around the resulting system with nitrogen, adding a water soluble radical polymerization initiator thereto, and heating the system.

The radical polymerization initiator includes, for example, hydrogen peroxide, sodium persulfate, potassium persulfate, ammonium persulfate, 2,2'-azobis(2-amidinopropane) dihydrochloride, and t-butyl hydroperoxide. The polymerization initiator can be added in successive increments or all at one time.

The amount of the polymerization initiator to be added may be generally from 0.01 to 5 parts by weight, preferably from 0.1 to 3 parts by weight, relative to 100 parts by weight of the monomers in total. If the amount of the polymerization initiator is less than 0.01 parts by weight, the polymerization of the monomers could not be conducted efficiently, but if the amount of the polymerization initiator is more than 5 parts by weight, the cost of the catalyst increases to become uneconomical.

To promote the radical polymerization, a reducing agent, such as sodium pyrobisulfite, ferrous sulfate, copper sulfate, triethanolamine, glucose, formaldehyde sodium sulfoxylate, L-ascorbic acid or its salt, or sodium hydrogen sulfite, may be added to the polymerization system. Additionally, a chelating agent such as glycine, alanine, or sodium ethylenediamine tetraacetate may be added.

A chain transfer agent can be used to control the molecular weight of the copolymer produced. The chain transfer agent includes, for example, mercaptans such as t-dodecylmercaptan, n-tetradecylmercaptan, octylmercaptan, t-hexylmercaptan, and n-hexylmercaptan; halides such as ethylene bromide; hydrocarbons such as 9,10-dihydroanthracene, 1,4-cyclohexadiene and 1,4-dihydroanthracene; and heterocyclic compounds such as 2,5-dihydrofuran; as well as α-methylstyrene dimers, and xanthogen disulfides. In general, the chain transfer agent can be added in an amount of less than 10 parts by weight relative to 100 parts by weight of the monomers in total.

The polymerization temperature may be from about -50° to about 200° C., preferably from +50° to +150° C. The polymerization time may be from about 0.1 to about 30 hours, within which the radical polymerization shall be conducted.

It is desirable to successively add the monomers to the polymerization reactor. In order to produce a uniform composition of the monomers added and to remove the polymerization heat from the reactor, the time for the addition of the monomers should be from 0.5 to 5 hours, preferably from 1 to 3 hours.

It is desirable that the copolymer in the water-treating agent of the present invention, having the ability to inhibit scaling and to prevent fouling in water plants, comprises from about 5 to about 50 mol % of the unit derived from the conjugated dienesulfonic acid and/or its salt, from about 40 to about 90 mol % of the unit derived from the (meth)acrylic acid and/or its salt, and from about 1 to about 20 mol % of the unit derived from the 2-hydroxyethyl (meth)acrylate or the unit derived from the (meth)acrylamido-2-methylalkanesulfonic acid and/or its salt.

More preferably, the copolymer comprises from 10 to 30 mol % of the unit derived from the conjugated dienesulfonic acid and/or its salt, from 60 to 90 mol % of the unit derived from the (meth)acrylic acid and/or its salt, and from 2 to 15 mol % of the unit derived from the 2-hydroxyethyl (meth)acrylate or the unit derived from the (meth)acrylamido-2-methylalkanesulfonic acid and/or its salt.

In the resultant copolymer which is in the water-treating agent of the present invention having the ability to inhibit scaling and to prevent fouling in water systems, if the content of the unit derived from the conjugated dienesulfonic acid and/or its salt is less than about 5 mol % or more than about 50 mol %, the scaling-inhibition and fouling-prevention properties of the water-treating agent will be less effective. If the content of the unit derived from the (meth)acrylic acid and/or its salt in the resultant copolymer is less than about 40 mol % or more than about 90 mol %, the scaling-inhibition and fouling-prevention properties of the water-treating agent will be also less effective. If the content of the unit derived from the 2-hydroxyethyl (meth)acrylate or that of the unit derived from the (meth)acrylamido-2-methylalkanesulfonic acid and/or its salt is less than about 1 mol % or more than about 20 mol %, the scaling-inhibition and fouling-prevention properties of the water-treating agent will be also less effective.

The copolymer used in the water-treating agent of the present invention which has the ability to inhibit scaling and to prevent fouling in water system may comprise other monomer units, in addition to the units comprising the unit derived from the conjugated dienesulfonic acid and/or its salt of formula 1!, the unit derived from the (meth)acrylic acid and/or its salt of formula 2!, and the unit derived from the 2-hydroxymethyl (meth)acrylate of formula 3! or the unit derived from the (meth)acrylamido-2-methylalkanesulfonic acid and/or its salt of formula 4!.

The copolymers comprising additional monomer units to the above monomers 1!, 2!, 3!, and 4!, can be obtained by copolymerizing the monomer of formula 1!, the monomer of formula 2!, the monomer of formula 3! or 4!, and a monomer copolymerizable with these monomers, according to any convenient method such as aqueous solution polymerization.

Such monomers copolymerizable with the monomer of formula 1!, the monomer of formula 2! and the monomer of formula 3! or 4! include, for example, 3-allyloxy-2-hydroxypropanesulfonic acid, vinylsulfonic acid, acid phosphoxyethyl methacrylate, acid phosphoxyethyl acrylate, acid phosphoxy polyoxyethylene glycol monomethacrylate, (meth)acrylamide, (meth)acrylonitrile, methyl (meth)acrylate, glycidyl (meth)acrylate, N-methylol(meth)acrylamide, maleic acid, maleic anhydride, styrene, α-methylstyrene, vinyltoluene, p-methylstyrene, and vinyl acetate.

It is desirable that the ternary copolymer in the water-treating agent of the present invention, having the ability to inhibit scaling and to prevent fouling in water systems, has a weight average molecular weight of from about 500 to about 300,000, more preferably from about 5,000 to about 50,000.

If the copolymer in the water-treating agent has a weight average molecular weight of less than about 500, the scaling-inhibition and fouling-prevention effect of the agent will be lowered. If the copolymer has a weight average molecular weight of more than about 300,000, poor handling characteristics will result because the viscosity of the water-treating agent will be too high.

To use the water-treating agent of the present invention, the amount to be added to the water system is suitably selected. The amount depends on the quality of water to be treated therewith, which includes consideration of the parameters of the water's pH, hardness, alkalinity, and temperature. Additionally, the heat-transferring conditions in the system should be considered.

In general, the amount of the water-treating agent to be added should be from about 0.1 to about 1,000 mg/liter, in terms of the solid content of the copolymer in the water-treating agent. In most cases, the amount may be from about 1 to about 100 mg/liter, in terms of the solid content of the copolymer in the water-treating agent, in order for the water-treating agent to exhibit satisfactory scale inhibition and fouling-prevention.

The water-treating agent of the present invention can be used in, for example, boiler systems, cooling water systems, industrial water supply plants, dust collecting water plants, drainage systems and slug cooling systems in the iron industry, and ash cooling systems in garbage incinerators. The present invention can be used to prevent the systems from malfunctions caused by the adhesion or deposition of scale, sludge, or slime onto the surfaces of metal parts in the systems and malfunctions caused by the local corrosion that occurs in the areas under the adhered or deposited layers. Such malfunctions can be a result of the heat transfer failure and flow rate reduction caused by the adhered or deposited scale, sludge, or slime. The process of adding to such water systems the water-treating agent of the present invention having the ability to inhibit scaling and to prevent fouling is not specifically defined but is by any convenient means for users of such water systems.

For example, referring to FIG. 1, the water-treating agent of the present invention can be added to the blowdown tank 7 before the circulating pump 6 circulates water to heat exchangers 1-4. The water-treating agent of the present invention can be added thereto in one dose, in intermittent doses, or continuously.

The water-treating agent can be used alone. However, it is preferably used with a corrosion inhibitor to synergistically increase the corrosion inhibiting effect.

The corrosion inhibitor includes polyvalent metal salts such as zinc salts, nickel salts, molybdates and tungstates; phosphonates; azoles such as triazoles; phosphates such as orthophosphates and polyphosphates; phosphonocarboxylates; amines and phosphoric esters.

The corrosion inhibitor, if used, can be added to the copolymer of the present invention, in an amount of from about 0.1 to about 10 parts by weight relative to one part of the copolymer. To combine the inhibitor and the copolymer, predetermined amounts of each can be previously mixed to give one formulation which is added to the water systems, or alternatively, the inhibitor and the copolymer can be separately added to the water systems in such a manner that leads to predetermined amounts or concentrations of the two ingredients existing therein.

The water-treating agent of the present invention may further contain other water-treating agents. Such water-treating agents include other scaling-inhibition and fouling-prevention chemicals, microbicides (slime controlling agents), acids, and alkalis. The scaling-inhibition chemicals include, for example, polyacrylates, polyacrylamides and their partial hydrolysis products, maleic acid polymers, itaconic acid polymers, and binary acrylic copolymers comprising 2-hydroxyethyl methacrylate and hydroxyallyloxypropanesulfonic acid.

The microbicides (slime controlling agents) include, for example, chlorine compounds such as chlorine gas, sodium and potassium hypochlorite, and sodium chloroisocyanurate; inorganic and organic, bromine containing agents; organic nitrogen sulfur compounds; and quaternary ammonium salts.

The present invention is described in more detail below with reference to the following production examples and examples which, however, are not intended to restrict the scope of the present invention.

EXAMPLES

Production Example 1:

The three monomers of 189.1 g of isoprenesulfonic acid (commercially-available product with an acid content of 40% by weight), 200.3 g of acrylic acid (commercially available product with an acid content of 80% by weight), and 40.6 g of 2-hydroxyethyl methacrylate (commercially available product with an ester content of 95% by weight) were mixed to prepare an aqueous monomer solution comprising the monomers. The molar percent ratio of isoprenesulfonic acid/acrylic acid/2-hydroxyethyl methacrylate in the aqueous solution was 15/75/10.

228.7 g of water and 13.7 g of 30 wt. %-hydrogen peroxide aqueous solution were put into a one liter, four neck separable flask. The flask was equipped with a stirrer, a reflux condenser, a dropping funnel and a nitrogen gas introducing tube. The aqueous monomer solution previously prepared above was dropwise added into the flask over a period of 2 hours, under inert atmosphere, while maintaining the inner temperature of the flask at 100° C., to cause polymerization.

After the addition of the monomer solution, the polymerization was conducted further for one hour, and then 40.8 g of a 48 wt. %-sodium hydroxide aqueous solution was added to the reaction mixture to partially neutralize it. This process yielded a ternary polymer having a number average molecular weight of 14,000. The resulting copolymer was used in Example 2.

Using the same procedure as above but varying the compositional ratio of the initial monomers to be reacted, various copolymers having different monomer compositions were obtained as shown in Tables 1 to 4.

IA) Test for Gelling of Scaling-inhibition and fouling-prevention Agent with Calcium Ion

Example 1:

The ingredients of 1) demineralized water, 2) a pH buffering solution comprising boric acid and sodium borate, 3) a solution of the scaling-inhibition and fouling-prevention agent comprising the sodium salt of the isoprenesulfonic acid/acrylic acid/2-hydroxyethyl methacrylate (20/75/5, by mol %) ternary copolymer having a weight average molecular weight of 14,000, and 4) a solution of calcium chloride were put into a 500 ml conical beaker in that order, to prepare 500 ml of a test liquid having a pH of 8.5, a solid content of the scaling-inhibition and fouling-prevention agent of 100 mg/liter, and a calcium hardness, in terms of CaCO₃ content, of 50 mg/liter.

By varying the amount of the calcium chloride solution added, the same process as above was repeated to prepare various test liquids of 500 ml each, having the calcium hardness values, in terms of CaCO₃ content, of 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, or 1200 mg/liter.

The conical beakers were each sealed with a polyethylene film, and left in a water bath filled with water having a controlled temperature of 90° C., for 1 hour. After this treatment, the degree of turbidity of each test liquid was measured. The turbidity results from any gel formed in each test liquid through the bonding of calcium ions to the copolymer of the scaling-inhibition and fouling-prevention agent.

The test liquids having a calcium concentration, the calcium hardness values in terms of CaCO₃, of 900 mg/liter or less did not become turbid, while those having a calcium concentration of 1000 mg/liter or more became turbid.

The minimum calcium hardness (calcium concentration) that would make the test liquid cloudy (turbid) was defined to be the anti-gelling concentration for the copolymer tested. According to this definition, the anti-gelling concentration for the copolymer of the scale inhibiting and fouling-prevention agent tested in this example was 1000 mg of CaCO₃ /liter.

Example 2:

The same experiment as in Example 1 was repeated, except that a solution of the sodium salt of the isoprenesulfonic acid/acrylic acid/2-hydroxyethyl methacrylate (15/75/10, by mol %) ternary copolymer having a weight average molecular weight of 14,000 was used as the scaling-inhibition and fouling-prevention agent. The anti-gelling concentration for the inhibiting retarding and fouling-prevention agent tested in this example was 500 mg of CaCO₃ /liter.

Comparative Example 1:

The same experiment as in Example 1 was repeated, except that a solution of the sodium salt of the isoprenesulfonic acid/acrylic acid (25/75, by mol %) binary copolymer having a weight average molecular weight of 10,000 was used as the scale retarding and soil preventing agent. The anti-gelling concentration for the scaling-inhibition and fouling-prevention agent tested in this comparative example was 400 mg of CaCO₃ /liter.

Comparative Example 2:

The same experiment as in Example 1 was repeated, except that a solution of the sodium salt of the isoprenesulfonic acid/acrylic acid (25/75, by mol %) binary copolymer having a weight average molecular weight of 15,000 was used as the scaling-inhibition and fouling-prevention agent. The anti-gelling concentration for the scaling-inhibition and fouling-prevention agent tested in this comparative example was 400 mg of CaCO₃ /liter.

Comparative Example 3:

The same experiment as in Example 1 was repeated, except that a solution of a sodium polyacrylate having a weight average molecular weight of 5,000 was used as the scale retarding and soil preventing agent. The anti-gelling concentration for the scale inhibiting and fouling-prevention agent tested in this comparative example was 100 mg of CaCO₃ /liter.

The results of Examples 1 and 2, and Comparative Examples 1 to 3 are shown in Table 1.

                                      TABLE 1                                      __________________________________________________________________________                                         Anti-gelling                               Scaling-inhibition           Amount Added                                                                          Concentration                              and fouling-  IPS/AA/HEMA    (mg of solid                                                                          (mg of                                     prevention Agent                                                                             (by mol)                                                                              Molecular Weight                                                                       content/liter)                                                                        CaCO.sup.3 /liter)                         __________________________________________________________________________     Example 1                                                                            IPS/AA/HEMA                                                                            20/75/5                                                                               14,000  100    1000                                             Copolymer.sup.(1)                                                        Example 2                                                                            IPS/AA/HEMA                                                                            15/75/10                                                                              14,000  100    500                                              Copolymer.sup.(1)                                                        Comparative                                                                          IPS/AA  25/75/0                                                                               10,000  100    400                                        Example 1                                                                            Copolymer.sup.(1)                                                        Comparative                                                                          IPS/AA  25/75/0                                                                               15,000  100    400                                        Example 2                                                                            Copolymer.sup.(1)                                                        Comparative                                                                          Sodium  0/100/0                                                                                5,000  100    100                                        Example 3                                                                            Polyacrylate                                                             __________________________________________________________________________      Notes:                                                                         .sup.(1) Sodium Salt                                                           IPS: Isoprenesulfonic Acid                                                     AA: Acrylic Acid                                                               HEMA: 2Hydroxyethyl Methacrylate                                         

A higher anti-gelling concentration value is desirable because more scaling-inhibition and fouling-prevention agent can be used for a given water hardness. Further, the scaling-inhibition and fouling-prevention agent with the higher anti-gelling value can be used over a wider range of water hardnesses.

The scaling-inhibition and fouling-prevention agent, for which the anti-gelling concentration is higher, can be more stably dissolved in water having a high calcium hardness while still exhibiting a greater effectiveness for scaling-inhibition and fouling-prevention.

It is apparent from the results of the above examples and comparative examples that the scaling-inhibition and fouling-prevention agents of the present invention, comprising in the examples of an isoprenesulfonic acid/acrylic acid/2-hydroxyethyl methacrylate ternary copolymer are superior to the prior art. The present invention examples exhibit higher anti-gelling ability than the comparative examples of the prior art.

Therefore, the scaling-inhibition and fouling-prevention agents of the present invention can be dissolved more stably in water having a higher calcium hardness than the prior art agents such as sodium polyacrylate or the isoprenesulfonic acid/acrylic acid copolymer.

IB) Test for Preventing Precipitation of Calcium Phosphate

Example 3:

The ingredients of 1) demineralized water, 2) a pH buffering solution comprising boric acid and sodium borate, 3) a solution of calcium chloride, 4) a solution of a scaling-inhibition and fouling-prevention agent comprising the sodium salt of an isoprenesulfonic acid/acrylic acid/2-hydroxyethyl methacrylate (20/75/5, by mol %) ternary copolymer having a weight-average molecular weight of 14,000, and 5) a solution of sodium phosphate were put into a 500-ml conical beaker in that order, to prepare 500 ml of a test liquid having a pH of 8.6, a solid content of the scaling-inhibition and fouling-preventing agent of 8 mg/liter, a calcium hardness, in terms of CaCO₃ content, of 100 mg/liter, and a phosphate ion concentration, in terms of PO₄ ³⁻, of 10 mg/liter.

The conical beaker was sealed with a polyethylene film, and left in a water bath filled with water having a controlled temperature of 60° C. After 40 hours, the test liquid was taken out and filtered through a filer paper having a pore diameter of 0.1 μm, and the phosphate ion concentration which remained in the resulting filtrate was measured to be 9.5 mg PO₄ ³⁻ /liter.

Example 4:

The same experiment as in Example 3 was repeated, using the same scaling-inhibition and fouling-prevention agent as that used in Example 3, except that the concentration of the agent was, in terms of the solid content, 6 mg/liter. The phosphate ion concentration which remained in the filtrate was 4.2 mg PO₄ ³⁻ /liter.

Example 5:

The same experiment as in Example 3 was repeated, except that a solution of the sodium salt of an isoprenesulfonic acid/acrylic acid/2-hydroxyethyl methacrylate (15/75/10, by mol %) ternary copolymer having a weight average molecular weight of 14,000 was used as the scaling-inhibition and fouling-prevention agent with the concentration, in terms of the solid content, of the agent being 8 mg/liter. The phosphate ion concentration which remained in the filtrate was 9.1 mg PO₄ ³⁻ /liter.

Example 6:

The same experiment as in Example 3 was repeated, using the same scaling-inhibition and fouling-prevention agent as that used in Example 5 except that the concentration, in terms of the solid content, of the agent was changed to 6 mg/liter. The phosphate ion concentration which remained in the filtrate was 2.8 mg PO₄ ³⁻ /liter.

Comparative Example 4:

The same experiment as in Example 3 was repeated, except that a solution of the sodium salt of an isoprenesulfonic acid/acrylic acid (25/75, by mol %) binary copolymer having a weight average molecular weight of 15,000 was used as the scaling-inhibition and the fouling-prevention agent and that the concentration, in terms of the solid content, of the agent was 12 mg/liter. The phosphate ion concentration which remained in the filtrate was 9.2 mg PO₄ ³⁻ /liter.

Comparative Example 5:

The same experiment as in Example 3 was repeated, except that the same scaling-inhibition and fouling-prevention agent as that used in Comparative Example 4 was used and that the concentration of the agent was varied to 10 mg, in terms of the solid content, per liter. The phosphate ion concentration which remained in the filtrate was 6.3 mg PO₄ ³⁻ /liter.

Comparative Example 6:

The same experiment as in Example 3 was repeated, using the same scaling-inhibition and fouling-prevention agent as that used in Comparative Example 4 with the concentration, in terms of the solid content, of the agent being 8 mg/liter. The phosphate ion concentration which remained in the filtrate was 3.2 mg PO₄ ³⁻ /liter.

Comparative Example 7:

The same experiment as in Example 3 was repeated, except that a solution of a sodium polyacrylate having a weight average molecular weight of 5,000 was used as the scaling-inhibition and fouling-prevention agent and that the concentration, in terms of the solid content, of the agent was 12 mg/liter. The phosphate ion concentration which remained in the filtrate was 2.5 mg PO₄ ³⁻ /liter.

Comparative Example 8:

The same experiment as in Example 3 was repeated, except that the same scaling-inhibition and fouling-prevention agent as that used in Comparative Example 7 was used with the concentration, in terms of the solid content, of the agent being 8 mg/liter. The phosphate ion concentration which remained in the filtrate was 1.0 mg PO₄ ³⁻ /liter.

Comparative Example 9:

The same experiment as in Example 3 was repeated, except that no scaling-inhibition and fouling-prevention agent was added. The phosphate ion concentration which remained in the filtrate was 0.3 mg PO₄ ³⁻ /liter.

The results of Examples 3 to 6 and Comparative Examples 4 to 9 are shown in Table 2.

                                      TABLE 2                                      __________________________________________________________________________     Scaling-inhibition           Amount Added                                                                          Filtrate Phosphate                         and fouling-  IPS/AA/HEMA    (mg of solid                                                                          Ion Concentration                          prevention Agent                                                                             (by mol)                                                                              Molecular Weight                                                                       content/liter)                                                                        (mg PO.sub.4.sup.3- /liter)                __________________________________________________________________________     Example 3                                                                            IPS/AA/HEMA                                                                            20/75/5                                                                               14,000  8      9.5                                              Copolymer.sup.(1)                                                        Example 4                                                                            IPS/AA/HEMA                                                                            20/75/5                                                                               14,000  6      4.2                                              Copolymer.sup.(1)                                                        Example 5                                                                            IPS/AA/HEMA                                                                            15/75/10                                                                              14,000  8      9.1                                              Copolymer.sup.(1)                                                        Example 6                                                                            IPS/AA/HEMA                                                                            20/75/5                                                                               14,000  6      2.8                                              Copolymer.sup.(1)                                                        Comparative                                                                          IPS/AA  25/75/0                                                                               15,000  12     9.2                                        Example 4                                                                            Copolymer.sup.(1)                                                        Comparative                                                                          IPS/AA  25/75/0                                                                               15,000  10     6.3                                        Example 5                                                                            Copolymer.sup.(1)                                                        Comparative                                                                          IPS/AA  25/75/0                                                                               15,000  8      3.2                                        Example 6                                                                            Copolymer.sup.(1)                                                        Comparative                                                                          Sodium  0/100/0                                                                                5,000  12     2.5                                        Example 7                                                                            Polyacrylate                                                             Comparative                                                                          Sodium  0/100/0                                                                                5,000  8      1.0                                        Example 8                                                                            Polyacrylate                                                             Comparative                                                                          Not Added.                                                                             --     --      0      0.3                                        Example 9                                                                      __________________________________________________________________________      Notes:                                                                         .sup.(1) Sodium SaIt                                                           IPS: Isoprenesulfonic Acid                                                     AA: Acrylic Acid                                                               HEMA: 2Hydroxyethyl Methacrylate                                         

A high phosphate ion concentration which remains in the filtrate is desirable. The most effective scaling-inhibition and fouling-preventing agent would cause the phosphate ion content of the filtrate from the test liquid to be near to the original phosphate ion content of 10 mg PO₄ ³⁻ /liter.

The more effective scaling-inhibition and fouling-preventing agent results in the less precipitation of calcium phosphate in the above test procedure. As a consequence, the less calcium phosphate precipitated results in more phosphate ions remaining in solution. Accordingly, the more effective agent leads to the higher phosphate ion content of the filtrate from the test liquid.

It is clear that on the other hand, if the effect of the scaling-inhibition and fouling-prevention agent tested against the precipitation of calcium phosphate is smaller, the test liquid to which the agent was added would produce a larger amount of calcium phosphate precipitate. Since the precipitate which contains phosphate is removed through the filtration of the test liquid containing the agent, the filtrate would have a smaller phosphate ion content.

From the results in Table 2, it can be seen that, when the scaling-inhibition and fouling-prevention agent of the present invention comprising an isoprenesulfonic acid/acrylic acid/2-hydroxyethyl methacrylate copolymer was added to the test liquid in an amount of 8 mg, in terms of the solid content of the agent, per liter of the test liquid, the phosphate ion concentration in the filtrate was larger than 9 mg PO₄ ³⁻ /liter. This verifies the excellent effectiveness of the agent against the precipitation of calcium phosphate in the test liquid or, that is, against the formation of scale.

In comparison, when the comparative agent comprising an isoprenesulfonic acid/acrylic acid copolymer was added to the same test liquid in an amount of 8 mg, in terms of the solid content of the agent, per liter of the test liquid, the phosphate ion concentration in the filtrate was only 3.2 mg PO₄ ³⁻ /liter. Thus, there is a significant difference between the scaling-inhibition and fouling-prevention agent of the present invention and the comparative agent in the ability to prevent the precipitation of calcium phosphate.

The comparative agent required addition in an amount of 12 mg, in terms of the solid content of the agent, per liter of the test liquid, to make the phosphate ion concentration in the filtrate larger than 9 mg PO₄ ³⁻ /liter. With regard the other comparative agent comprising a sodium polyacrylate, even when it was added to the same test liquid in an amount of 12 mg, in terms of the solid content of the agent, per liter of the test liquid, the phosphate ion concentration in the filtrate was only 2.5 mg PO₄ ³⁻ /liter.

Hence, the agent of the present invention is more effective at preventing scaling and fouling.

IC) Test for Preventing Precipitation of Zinc Phosphate

Example 7:

The components of 1) demineralized water, 2) a solution of calcium chloride, 3) a solution of a scaling-inhibition and fouling-prevention agent comprising the sodium salt of an isoprenesulfonic acid/acrylic acid/2-hydroxyethyl methacrylate (20/75/5, by mol %) ternary copolymer having a weight average molecular weight of 14,000, 4) a solution of zinc chloride, and 5) a solution of sodium hydrogencarbonate were put into a 500 ml conical beaker in that order. Subsequently, an aqueous solution of 1 wt. %-sodium hydroxide was added thereto to adjust the pH of the resulting mixture. Thus, 500 ml of a test liquid was prepared having a pH of 8.6, a solid content of 4 mg/liter of the scaling-inhibition and soil preventing agent, a calcium hardness, in terms of CaCO₃ content, of 100 mg/liter, a total alkalinity, in terms of CaCO₃ content, of 100 mg/liter, a phosphate ion concentration, in terms of PO₄ ³⁻ of 6.0 mg/liter, and a zinc ion concentration, in terms of Zn²⁺, of 3.5 mg/liter. The total alkalinity refers to the total acids consumption of a sample titrated by acid to a pH of 4.8 from the alkaline side.

The conical beaker was sealed with a polyethylene film, and left in a water bath filled with water having a controlled temperature of 60° C. After 40 hours, the test liquid was taken out and filtered through a filter paper having a pore diameter of 0.1 μm. The phosphate ion concentration and the zinc ion concentration in total which remained in the resulting filtrate were measured to be 9.4 mg/liter.

Comparative Example 10:

The same experiment as in Example 7 was repeated except that a solution of the sodium salt of an isoprenesulfonic acid/acrylic acid (25/75, by mol %) binary copolymer having a weight-average molecular weight of 22,000 was used as the scaling-inhibition and fouling-prevention and that the concentration of the agent was 4 mg, in terms of the solid content, per liter. The sum of the phosphate ion concentration and the zinc ion concentration which remained in the filtrate was 9.0 mg/liter.

Comparative Example 11:

The same experiment as in Example 7 was repeated except that a solution of a sodium polyacrylate having a weight-average molecular weight of 5,000 was used as the scaling-inhibition and fouling-prevention agent with a concentration of the agent of 10 mg, in terms of the solid content, per liter. The sum of the phosphate ion concentration and the zinc ion concentration which remained in the filtrate was 3.5 mg/liter.

Comparative Example 12:

The same experiment as in Example 7 was repeated except that no scaling-inhibition and fouling-prevention agent was added. The sum of the phosphate ion concentration and the zinc ion concentration which remained in the filtrate was 0.2 mg/liter.

The results of Example 7 and Comparative Examples 10 to 12 are shown in Table 3.

                                      TABLE 3                                      __________________________________________________________________________                                         Sum of Phosphate                                                               Ion Concentration                                                              and Zinc Ion                               Scaling-inhibition           Amount Added                                                                          Concentration                              and fouling-  IPS/AA/HEMA    (mg of solid                                                                          Remaining                                  prevention Agent                                                                             (by mol)                                                                              Molecular Weight                                                                       content/liter)                                                                        (mg/liter)                                 __________________________________________________________________________     Example 7                                                                            IPS/AA/HEMA                                                                            20/75/5                                                                               14,000  4      9.4                                              Copolymer.sup.(1)                                                        Comparative                                                                          IPS/AA  25/75/0                                                                               22,000  4      9.0                                        Example 10                                                                           Copolymer.sup.(1)                                                        Comparative                                                                          Sodium  0/100/0                                                                                5,000  10     3.5                                        Example 11                                                                           Polyacrylate                                                             Comparative                                                                          Not added.                                                                             --     --      0      0.2                                        Example 12                                                                     __________________________________________________________________________      Notes:                                                                         .sup.(1) Sodium Salt                                                           IPS: Isoprenesulfonic Acid                                                     AA: Acrylic Acid                                                               HEMA: 2Hydroxyethyl Methacrylate                                         

A high sum of the phosphate ion content and the zinc ion content which remains in the filtrate is desirable. The most effective scaling-inhibition and fouling-preventing agent would cause the total phosphate ion and zinc ion content of the filtrate from the test liquid to be near to the sum of the phosphate ion content and the zinc ion content of the original test liquid, which is 9.5 mg/liter.

The more effective scaling-inhibition and fouling-preventing agent results in the less precipitation of zinc phosphate in the above test procedure. As a consequence, the less zinc phosphate precipitated results in more phosphate and zinc ions remaining in solution. Accordingly, the more effective agent leads to the higher total zinc and phosphate ion content of the filtrate from the test liquid.

It is clear that on the other hand, if the effect of the scaling-inhibition and fouling-prevention agent tested against the precipitation of zinc phosphate is smaller, the test liquid to which the agent was added would produce a larger amount of zinc phosphate precipitate. Since the precipitate which contains zinc and phosphate is removed through the filtration of the test liquid containing the agent, the filtrate would have a smaller total zinc and phosphate ion content.

From the results in Table 3, it can be seen from examination of Example 7 and Comparative Example 10, that both the addition of the scaling-inhibition and fouling-prevention agent of the present invention comprising an isoprenesulfonic acid/acrylic acid/2-hydroxyethyl methacrylate ternary copolymer to the test liquid in an amount of 4 mg, in terms of the solid content of the agent, per liter of the test liquid, and the addition of the comparative agent comprising an isoprenesulfonic acid/acrylic acid copolymer, to the test liquid in the same amount, resulted in almost the same total amount of phosphate ion and zinc ion concentration which remained in the filtrate in each, which was about 9.0 mg/liter.

This shows that the two agents have almost the same effect against the precipitation of zinc phosphate in the test liquid. However, as seen from the results in Table 2, the scaling-inhibition and fouling-prevention agent of the present invention comprising an isoprenesulfonic acid/acrylic acid/2-hydroxyethyl methacrylate is more effective against the precipitation of calcium phosphate than that of the comparative agent comprising an isoprenesulfonic acid/acrylic acid.

Therefore, it is apparent that the scaling-inhibition and fouling-prevention agent of the present invention is preferable to the comparative agent because the present invention is more effectively applicable to more systems than the comparative agent.

Regarding the other comparative agent of a sodium polyacrylate, even when it was added to the test liquid in an amount in terms of the solid content of the agent of 10 mg/liter of the test liquid, the sum of the phosphate ion concentration and the zinc ion concentration which remained in the filtrate was only 3.5 mg/liter.

ID) Test for Preventing Precipitation of Iron Oxide and Iron Hydroxide

Example 8:

The components of 1) demineralized water, 2) a solution of a scaling-inhibition and fouling-prevention agent comprising the sodium salt of an isoprenesulfonic acid/acrylic acid/2-hydroxyethyl methacrylate (20/75/5, by mol %) ternary copolymer having a weight-average molecular weight of 14,000, 3) a solution of sodium hydrogencarbonate, 4) a solution of sodium silicate No. 3, 5) a solution of calcium chloride, 6) a solution of magnesium sulfate, and 7) a solution of ferric chloride were put into a 500-ml conical beaker in that order. Next, an aqueous solution of 1 wt. % sulfuric acid was added thereto to adjust the pH of the resulting mixture.

Thus 500 ml of a test liquid was prepared having a pH of 8.8, a solid content of the scaling-inhibition and fouling-preventing agent of 5.0 mg/liter, a calcium hardness, in terms of CaCO₃ content, of 250 mg/liter, a magnesium hardness, in terms of CaCO₃ content, of 100 mg/liter, a total alkalinity, in terms of CaCO₃ content, of 250 mg/liter, a silica content, in terms of SiO₂, of 100 mg/liter and a total iron content, in terms of Fe, of 10 mg/liter. The total alkalinity refers to the total acids consumption of a sample titrated by acid to a pH of 4.8 from the alkaline side. It is common practice in water treatment to express parameter values in terms of CaCO₃ content.

The conical beaker was sealed with a polyethylene film, and left in a water bath filled with water having a controlled temperature of 30° C., for 20 hours. Afterwards, the beaker was taken out, and the dissolved iron content of the supernatant thus separated in the beaker was measured to be 10.0 mg Fe/liter.

Example 9:

The same experiment as in Example 8 was repeated, except that a solution of the sodium salt of an isoprenesulfonic acid/acrylic acid/2-hydroxyethyl methacrylate (15/75/10, by mol %) ternary copolymer having a weight average molecular weight of 14,000 was used as the scaling-inhibition and fouling-prevention agent and that the concentration of the agent was 5.0 mg, in terms of the solid content, per liter. The dissolved iron content of the supernatant was 10.0 mg Fe/liter.

Comparative Example 13:

The same experiment as in Example 8 was repeated, except that a solution of the sodium salt of an isoprenesulfonic acid/acrylic acid (25/75, by mol %) binary copolymer having a weight-average molecular weight of 16,000 was used as the scaling-inhibition and the fouling-prevention agent and that the concentration of the agent was 7.5 mg, in terms of the solid content, per liter. The dissolved iron content of the supernatant was 10.0 mg Fe/liter.

Comparative Example 14:

The same experiment as in Example 8 was repeated, except that the same scaling-inhibition and fouling-prevention agent was used as that in Comparative Example 13 and that the concentration of the agent was 5.0 mg, in terms of the solid content, per liter. The dissolved iron content of the supernatant was 7.8 mg Fe/liter.

Comparative Example 15:

The same experiment as in Example 8 was repeated, except that a solution of the sodium salt of an isoprenesulfonic acid/acrylic acid (25/75, by mol %) binary copolymer having a weight average molecular weight of 22,000 was used as the scale inhibiting and fouling-preventing agent with a concentration of the agent of 7.5 mg, in terms of the solid content, per liter. The dissolved iron content of the supernatant was 10.0 mg Fe/liter.

Comparative Example 16:

The same experiment as in Example 8 was repeated, except that the same scaling-inhibition and fouling-prevention agent was used as that of Comparative Example 15 with a concentration of the agent of 5.0 mg, in terms of the solid content, per liter. The dissolved iron content of the supernatant was 8.0 mg Fe/liter.

Comparative Example 17:

The same experiment as in Example 8 was repeated, except that a solution of sodium hexametaphosphate with a concentration of 10.0 mg, in terms of the solid content, per liter was used as the scaling-inhibition and fouling-prevention agent. The dissolved iron content of the supernatant was 3.3 mg Fe/liter.

Comparative Example 18:

The same experiment as in Example 8 was repeated, except that a solution of sodium hexametaphosphate was used as the scaling-inhibition and fouling-prevention agent and that the concentration of the agent was 7.5 mg, in terms of the solid content, per liter. The dissolved iron content of the supernatant was 2.4 mg Fe/liter.

Comparative Example 19:

The same experiment as in Example 8 was repeated, except that a solution of a sodium polyacrylate having a weight average molecular weight of 5,000 was used as the scaling-inhibition and fouling-prevention agent with a concentration of 10.0 mg, in terms of the solid content, per liter. The dissolved iron content of the supernatant was 6.0 mg Fe/liter.

Comparative Example 20:

The same experiment as in Example 8 was repeated, except that no scaling-inhibition and fouling-prevention agent was added. The dissolved iron content of the supernatant was 0.4 mg Fe/liter.

The results of Examples 8 to 9 and Comparative Examples 13 to 20 are shown in Table 4.

                                      TABLE 4                                      __________________________________________________________________________                                         Disolved Iron                              Scaling-inhibition           Amount Added                                                                          Concentration                              and fouling-  IPS/AA/HEMA    (mg of solid                                                                          Remaining                                  prevention Agent                                                                             (by mol)                                                                              Molecular Weight                                                                       content/liter)                                                                        (mg Fe/liter)                              __________________________________________________________________________     Example 8                                                                            IPS/AA/HEMA                                                                            20/75/5                                                                               14,000  5.0    10.0                                             Copolymer.sup.(1)                                                        Example 9                                                                            IPS/AA/HEMA                                                                            15/75/10                                                                              14,000  5.0    10.0                                             Copolymer.sup.(1)                                                        Comparative                                                                          IPS/AA  25/75/0                                                                               16,000  7.5    10.0                                       Example 13                                                                           Copolymer.sup.(1)                                                        Comparative                                                                          IPS/AA  25/75/0                                                                               16,000  5.0    7.8                                        Example 14                                                                           Copolymer.sup.(1)                                                        Comparative                                                                          IPS/AA  25/75/0                                                                               22,000  7.5    10.0                                       Example 15                                                                           Copolymer.sup.(1)                                                        Comparative                                                                          IPS/AA  25/75/0                                                                               22,000  5.0    8.0                                        Example 16                                                                           Copolymer.sup.(1)                                                        Comparative                                                                          Sodium Hexa-                                                                           --     --      10.0   3.3                                        Example 17                                                                           metaphosphate                                                            Comparative                                                                          Sodium Hexa-                                                                           --     --      7.5    2.4                                        Example 18                                                                           metaphosphate                                                            Comparative                                                                          Sodium  0/100/0                                                                                5,000  10.0   6.0                                        Example 19                                                                           Polyacrylate                                                             Comparative                                                                          Not Added.                                                                             --     --      0      0.4                                        Example 20                                                                     __________________________________________________________________________      Notes:                                                                         .sup.(1) Sodium Salt                                                           IPS: Isoprenesulfonic Acid                                                     AA: Acrylic Acid                                                               HEMA: 2Hydroxyethyl Methacrylate                                         

If there is no scaling-inhibition and fouling-prevention agent added to the test liquid or if the effect of any added scaling-inhibition and fouling-prevention agent is not satisfactory, the iron component in the test liquid would precipitate in the form of iron oxide hydrate or iron hydroxide.

Therefore, the effectiveness can be evaluated, of the scaling-inhibition and fouling-prevention agent added to the test liquid, by measuring the dissolved iron content in the supernatant. An effective agent would disperse the iron oxide or iron hydroxide to prevent precipitate formation. Accordingly, an effective agent would lead to a high concentration of iron in the test liquid which can be determined from the dissolved iron content remaining in the supernatant separated from the test liquid to which the agent was added.

The scaling-inhibition and fouling-prevention agent of the present invention comprising an isoprenesulfonic acid/acrylic acid/2-hydroxyethyl methacrylate ternary copolymer, when added to the test liquid in an amount of 5 mg, in terms of the solid content thereof, per liter, inhibited the precipitation of iron to the extent of 10 mg/liter remaining in the supernatant, while acting to completely disperse and keep it in water in the test liquid. Therefore, any concentration of iron less than 10 mg/liter in the test system would dissolve.

In comparison, however, when the comparative agent comprising an isoprenesulfonic acid/acrylic acid copolymer was added to the same test liquid in an amount of 5 mg, in terms of the solid content thereof, per liter, the solution of iron could not reach 10 mg/liter. Instead, the iron concentration remaining in the supernatant was only 7.8 mg/liter before iron was precipitated out, thus indicating that a detrimentally substantial amount of iron was precipitated out.

In order to inhibit the precipitation of iron to lead to a concentration of iron of 10 mg/liter in the test liquid, it was necessary to add 7.5 mg/liter, in terms of the solid content, of the comparative agent to the test liquid. Accordingly, the present invention is superior to the comparison isoprenesulfonic acid/acrylic acid copolymer for dispersing iron oxide and iron hydroxide in water.

The other comparative agents comprising sodium hexametaphosphate or sodium polyacrylate of the prior art could not inhibit the precipitation of iron to the extent of 10 mg/liter in the test liquid even when such comparative examples were added to the test liquid in an amount of 10 mg, in terms of the solid content, per liter.

From these results, it is apparent that the scaling-inhibition and fouling-prevention agent of the present invention is much more effective for dispersing iron oxide and iron hydroxide in water than the comparative agents comprising sodium hexametaphosphate or sodium polyacrylate.

Production Example 2:

The three monomers, 252.1 g of isoprenesulfonic acid (commercially-available product with an acid content of 40% by weight), 200.3 g of acrylic acid (commercially available product with an acid content of 80% by weight), and 31.4 g of acrylamido-2-methylpropanesulfonic acid (commercially available product with an acid content of 98% by weight), were mixed to prepare an aqueous monomer solution. The molar ratio of isoprenesulfonic acid/acrylic acid/acrylamido-2-methylpropanesulfonic acid in the aqueous monomer solution was 20/75/5.

228.7 g of water and 13.7 g of 30 wt. %-hydrogen peroxide aqueous solution were put into a one liter, four neck separable flask which was equipped with a stirrer, a reflux condenser, a dropping funnel and a nitrogen gas-introducing tube. The aqueous monomer solution that had been prepared above was added dropwise thereto over a period of 2 hours while keeping the inner temperature of the flask at 100° C. to perform polymerization. After the addition, the polymerization was conducted for one hour further. At the end of the hour, 67.3 g of a 48 wt. %-sodium hydroxide aqueous solution was added to the reaction mixture to partially neutralize the mixture. Thus was obtained a ternary copolymer having a number average molecular weight of 22,000. This particular ternary copolymer formed in this Production Example 2 was used below in Example 11.

Using the same process as above but changing the compositional ratio of the monomers reacted and changing the amount of hydrogen peroxide added, various copolymers having different monomer compositions were obtained as shown in Tables 5 to 8.

IIA) Test for Gelling of Scaling-inhibition and fouling-prevention Agent with Calcium Ion

Example 10:

The components of.

1) demineralized water,

2) a pH buffering solution comprising boric acid and sodium borate,

3) a scaling-inhibition and fouling-preventing agent comprising either

(A1) a solution of sodium salt of isoprenesulfonic acid/acrylic acid/2-hydroxyethyl methacrylate (20/75/5, by mol %) copolymer having a weight average molecular weight of 14,000 or

(B1) a solution of sodium salt of isoprenesulfonic acid/acrylic acid/acrylamido-2-methylpropanesulfonic acid (20/75/5, by mol %) copolymer having a weight average molecular weight of 15,000,

and

4) a solution of calcium chloride, were put into a 500-ml conical beaker in that order, to prepare 500 ml of a test liquid having a pH of 8.5, a solid content of the scaling-inhibition and fouling-prevention agent of 100 mg/liter, and a calcium hardness, in terms of CaCO₃ content, of 50 mg/liter.

By varying the amount of the calcium chloride solution added, the same process as in Example 10 above was repeated to prepare various test liquids of 500 ml each, having a calcium hardness, in terms of CaCO₃ content, of 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, and 1200 mg/liter.

The conical beakers each were sealed with a polyethylene film, and left in a water bath filled with water having a controlled temperature of 90° C., for 1 hour. After this treatment, the degree of turbidity of each test liquid was measured. The turbidity results from the gel formed by the bonding of calcium ions to the copolymer of the scaling-inhibition and fouling-prevention agent. The minimum calcium hardness (calcium concentration) that makes the test liquid cloudy (turbid) was defined to be the anti-gelling concentration for the particular copolymer sample tested.

The test samples comprising (A1) and having calcium concentrations, in terms of CaCO₃, of 900 mg/liter or less did not become turbid, while those comprising (A1) and having calcium concentrations, in terms of CaCO₃, of 1000 mg/liter or more did become turbid. According to the definition, the anti-gelling concentration for the copolymer of the scaling-inhibition and fouling-prevention agent (A1) tested herein was 1000 mg of CaCO₃ /liter.

On the other hand, the test liquids comprising (B1) and having calcium concentrations, in terms of CaCO₃, of 500 mg/liter or less did not become turbid, while those comprising (B1) and having calcium concentrations, in terms of CaCO₃, of 600 mg/liter or more did become turbid. The anti-gelling concentration for the copolymer of the scaling-inhibition and fouling-prevention agent (B1) tested herein was 600 mg of CaCO₃ /liter.

Example 11:

The same experiment as in Example 10 was repeated, except that a solution of the sodium salt of an isoprenesulfonic acid/acrylic acid/acrylamido-2-methylpropanesulfonic acid (20/75/5, by mol %) ternary copolymer having a weight average molecular weight of 22,000 was used as the scaling-inhibition and fouling-prevention agent. The anti-gelling concentration for the scaling-inhibition and fouling-prevention agent tested in this example was 600 mg of CaCO₃ /liter.

Comparative Example 21:

The same experiment as in Example 10 was repeated, except that a solution of the sodium salt of an isoprenesulfonic acid/acrylic acid (25/75, by mol %) binary copolymer having a weight average molecular weight of 10,000 was used as the scaling-inhibition and fouling-prevention agent. The anti-gelling concentration for the scaling-inhibition and fouling-prevention agent tested in this comparative example was 400 mg of CaCO₃ /liter.

Comparative Example 22:

The same experiment as in Example 10 was repeated, except that a solution of the sodium salt of an isoprenesulfonic acid/acrylic acid (25/75, by mol %) binary copolymer having a weight average molecular weight of 15,000 was used as the scaling-inhibition and fouling-prevention agent. The anti-gelling concentration for the scaling-inhibition and fouling-prevention agent tested in this comparative example was 400 mg of CaCO₃ /liter.

Comparative Example 23:

The same experiment as in Example 10 was repeated, except that a solution of a sodium polyacrylate having a weight average molecular weight of 5,000 was used as the scaling-inhibition and fouling-prevention agent. The anti-gelling concentration for the scaling-inhibition and fouling-prevention agent tested in this comparative example was 100 mg of CaCO₃ /liter.

The results of Examples 10 and 11 and Comparative Examples 21 to 23 are shown in Table 5.

                                      TABLE 5                                      __________________________________________________________________________                                         Anti-gelling                               Scaling-inhibition           Amount Added                                                                          Concentration                              and fouling-  IPS/AA/AMPS    (mg of solid                                                                          (mg of                                     prevention Agent                                                                             (by mol)                                                                              Molecular Weight                                                                       content/liter)                                                                        CaCO.sup.3 /liter)                         __________________________________________________________________________     Example 10                                                                           IPS/AA/AMPS                                                                            20/75/5                                                                               15,000  100    600                                              Copolymer.sup.(1)                                                        Example 11                                                                           IPS/AA/AMPS                                                                            20/75/5                                                                               22,000  100    600                                              Copolymer.sup.(1)                                                        Comparative                                                                          IPS/AA  25/75/0                                                                               10,000  100    400                                        Example 21                                                                           Copolymer.sup.(1)                                                        Comparative                                                                          IPS/AA  25/75/0                                                                               15,000  100    400                                        Example 22                                                                           Copolymer.sup.(1)                                                        Comparative                                                                          Sodium  0/100/0                                                                                5,000  100    100                                        Example 23                                                                           Polyacrylate                                                             __________________________________________________________________________      Notes:                                                                         .sup.(1) Sodium Salt                                                           IPS: Isoprenesulfonic Acid                                                     AA: Acrylic Acid                                                               AMPS: Acrylamido2-methylpropanesulfonic Acid                             

As previously discussed, the scaling-inhibition and fouling-prevention agent with the higher anti-gelling concentration can be more stably dissolved in water having a high calcium hardness, than the agent with the lower anti-gelling concentration, while at the same time showing more effective scaling-inhibition and fouling-prevention.

It can be seen from the results of the above examples and comparative examples that the scaling-inhibition and fouling-prevention agents of the present invention, each comprising an isoprenesulfonic acid/acrylic acid/acrylamido-2-methylpropanesulfonic acid ternary copolymer, exhibit a higher anti-gelling ability and therefore can be dissolved more stably in water having a high calcium hardness than the comparative agent comprising a sodium polyacrylate. The examples of the present invention similarly demonstrate higher anti-gelling concentrations than the other comparative prior art agents comprising an isoprenesulfonic acid/acrylic acid copolymer.

IIB) Test for Preventing Precipitation of Calcium Phosphate

Example 12:

The ingredients of 1) demineralized water, 2) a pH buffering solution comprising boric acid and sodium borate, 3) a solution of calcium chloride, 4) a solution of a scaling-inhibition and fouling-prevention agent comprising the sodium salt of an isoprenesulfonic acid/acrylic acid/acrylamido-2-methylpropanesulfonic acid (20/75/5, by mol %) ternary copolymer having a weight average molecular weight of 15,000, and 5) a solution of sodium phosphate were put into a 500-ml conical beaker, in that order, to prepare 500 ml of a test liquid having a pH of 8.6, a solid content of the scaling-inhibition and fouling-preventing agent of 8 mg/liter, a calcium hardness, in terms of CaCO₃ content, of 100 mg/liter, and a phosphate ion concentration, in terms of PO₄ ³⁻, of 10 mg/liter.

The conical beaker was sealed with a polyethylene film, and left in a water bath tilled with water having a controlled temperature of 60° C. After 40 hours, the test liquid was taken out and filtered through a filer paper having a pore diameter of 0.1 μm, and the phosphate ion concentration which remained in the resulting filtrate was measured to be 9.4 mg PO₄ ³⁻ /liter.

Example 13:

The same experiment as in Example 12 was repeated, using the same scaling-inhibition and fouling-prevention agent as that used in Example 12, except that the concentration of the agent was changed to 6 mg, in terms of the solid content, per liter. The phosphate ion concentration which remained in the filtrate was 2.4 mg PO₄ ³⁻ /liter.

Example 14:

The same experiment as in Example 12 was repeated, except that a solution of the sodium salt of an isoprenesulfonic acid/acrylic acid/acrylamido-2-methylpropanesulfonic acid (20/75/5, by mol %) ternary copolymer having a weight average molecular weight of 22,000 was used as the scaling-inhibition and fouling-prevention agent with a concentration of the agent of 8 mg, in terms of the solid content, per liter. The phosphate ion concentration which remained in the filtrate was 9.2 mg PO₄ ³⁻ /liter.

Example 15:

The same experiment as in Example 12 was repeated, except that the same scaling-inhibition and fouling-prevention agent as that used in Example 14 was used and that the concentration of the agent was 6 mg, in terms of the solid content, per liter. The phosphate ion concentration remained in the filtrate was 1.6 mg PO₄ ³⁻ /liter.

Comparative Example 24:

The same experiment as in Example 12 was repeated, except that a solution of the sodium salt of an isoprenesulfonic acid/acrylic acid (25/75, by mol %) binary copolymer having a weight average molecular weight of 15,000 was used as the scaling-inhibition and the fouling-prevention agent and that the concentration of the agent was 12 mg, in terms of the solid content, per liter. The phosphate ion concentration which remained in the filtrate was 9.2 mg PO₄ ³⁻ /liter.

Comparative Example 25:

The same experiment as in Example 12 was repeated, except that the same scaling-inhibition and fouling-prevention agent was used as that in Comparative Example 24 and that the concentration of the agent was 10 mg, in terms of the solid content, per liter. The phosphate ion concentration which remained in the filtrate was 6.3 mg PO₄ ³⁻ /liter.

Comparative Example 26:

The same experiment as in Example 12 was repeated, except that the same scaling-inhibition and fouling-prevention agent as that used in Comparative Example 24 was used and that the concentration of the agent was 8 mg, in terms of the solid content, per liter. The phosphate ion concentration which remained in the filtrate was 3.2 mg PO₄ ³⁻ /liter.

Comparative Example 27:

The same experiment as in Example 12 was repeated, except that a solution of a sodium polyacrylate having a weight-average molecular weight of 5,000 was used as the scaling-inhibition and fouling-prevention agent and that the concentration of the agent was 12 mg, in terms of the solid content, per liter. The phosphate ion concentration which remained in the filtrate was 2.5 mg PO₄ ³⁻ /liter.

Comparative Example 28:

The same experiment as in Example 12 was repeated, except that the same scaling-inhibition and fouling-prevention agent as that used in Comparative Example 27 was used with a concentration of 8 mg, in terms of the solid content, per liter. The phosphate ion concentration which remained in the filtrate was 1.0 mg PO₄ ³⁻ /liter.

Comparative Example 29:

The same experiment as in Example 12 was repeated, except that no scaling-inhibition and fouling-prevention agent was added. The phosphate ion concentration which remained in the filtrate was 0.3 mg PO₄ ³⁻ /liter.

The results of Examples 12 to 15 and Comparative Examples 24 to 29 are shown in Table 6.

                                      TABLE 6                                      __________________________________________________________________________                                         Phosphate Ion                              Scaling-inhibition           Amount Added                                                                          Concentration                              and Fouling-  IPS/AA/AMPS    (mg of solid                                                                          Remained (mg                               Prevention Agent                                                                             (by mol %)                                                                            Molecular Weight                                                                       content/liter)                                                                        PO.sub.4.sup.3- /liter)                    __________________________________________________________________________     Example 12                                                                           IPS/AA/AMPS                                                                            20/75/5                                                                               15,000  8      9.4                                              Copolymer.sup.(1)                                                        Example 13                                                                           IPS/AA/AMPS                                                                            20/75/5                                                                               15,000  5      2.4                                              Copolymer.sup.(1)                                                        Example 14                                                                           IPS/AA/AMPS                                                                            20/75/5                                                                               22,000  6      9.2                                              Copolymer.sup.(1)                                                        Example 15                                                                           IPS/AA/AMPS                                                                            20/75/5                                                                               22,000  6      1.6                                              Copolymer.sup.(1)                                                        Comparative                                                                          IPS/AA  25/75/0                                                                               15,000  12     9.2                                        Example 24                                                                           Copolymer.sup.(1)                                                        Comparative                                                                          IPS/AA  25/75/0                                                                               15,000  10     6.3                                        Example 25                                                                           Copolymer.sup.(1)                                                        Comparative                                                                          IPS/AA  25/75/0                                                                               15,000  8      3.2                                        Example 26                                                                           Copolymer.sup.(1)                                                        Comparative                                                                          Sodium  0/100/0                                                                                5,000  12     2.5                                        Example 27                                                                           Polyacrylate                                                             Comparative                                                                          Sodium  0/100/0                                                                                5,000  8      1.0                                        Example 28                                                                           Polyacrylate                                                             Comparative                                                                          Not Added.                                                                             --     --      0      0.3                                        Example 29                                                                     __________________________________________________________________________      Notes:                                                                         .sup.(1) Sodium Salt                                                           IPS: Isoprenesulfonic Acid                                                     AA: Acrylic Acid                                                               AMPS: Acrylamido2-methylpropanesulfonic Acid                             

As discussed previously, if the effect is larger from the scaling-inhibition and fouling-prevention agent tested against the precipitation of calcium phosphate, the test liquid to which the agent was added would produce a smaller amount of the calcium phosphate precipitate therein. Therefore, the phosphate ion content of the filtrate from the test liquid containing the more effective agent will be nearer to the original phosphate ion content of the test liquid which was 10 mg PO₄ ³⁻ /liter.

On the other hand, if the effect is smaller from the scaling-inhibition and fouling-prevention agent tested against the precipitation of calcium phosphate, the test liquid to which the less effective agent was added will produce a larger amount of the calcium phosphate precipitate therein. Since the calcium phosphate precipitate is removed through the filtration of the test liquid containing the agent, the filtrate will have a smaller phosphate ion content as a consequence.

From the results in Table 6, it is clear that, when the scaling-inhibition and fouling-prevention agent of the present invention comprising an isoprenesulfonic acid/acrylic acid/acrylamido-2-methylpropanesulfonic acid ternary copolymer was added to the test liquid in an amount of 8 mg, in terms of the solid content of the agent, per liter of the test liquid, the phosphate ion concentration in the filtrate was larger than 9 mg PO₄ ³⁻ /liter. This verities the excellent effectiveness of the agent of the present invention against the precipitation of calcium phosphate in the test liquid or, that is, against the formation of scale.

In comparison, when the comparative agent comprising an isoprenesulfonic acid/acrylic acid copolymer was added to the same test liquid in the same amount of 8 mg, in terms of the solid content of the agent, per liter of the test liquid, the phosphate ion concentration in the filtrate was only 3.2 mg PO₄ ³⁻ /liter. Thus, there is a significant difference between the scaling-inhibition and fouling-prevention agent of the present invention and the comparative agent in their ability to prevent the precipitation of calcium phosphate.

Only when the comparative agent was added in an increased amount of 12 mg, in terms of the solid content of the agent, per liter of the test liquid, did the phosphate ion concentration in the filtrate become larger than 9 mg PO₄ ³⁻ /liter.

Regarding the other comparative agent comprising a sodium polyacrylate, even when it was added to the same test liquid in an amount of 12 mg, in terms of the solid content of the agent, per liter of the test liquid, the phosphate ion concentration in the filtrate was nonetheless only 2.5 mg PO₄ ³⁻ /liter.

IIC) Test for Preventing Precipitation of Zinc Phosphate

Example 16:

The ingredients of 1) demineralized water, 2) a solution of calcium chloride, 3) a solution of a scaling-inhibition and fouling-prevention agent comprising the sodium salt of an isoprenesulfonic acid/acrylic acid/acrylamido-2-methylpropanesulfonic acid (20/75/5, by mol %) ternary copolymer having a weight average molecular weight of 22,000, 4) a solution of zinc chloride and 5) a solution of the sodium hydrogencarbonate were put into a 500-ml conical beaker in that order. Subsequently, an aqueous solution of 1 wt. %-sodium hydroxide was added thereto to adjust the pH of the resulting mixture.

Thus was prepared 500 ml of a test liquid having a pH of 8.6, a solid content of the scaling-inhibition and fouling-prevention agent of 4 mg/liter, a calcium hardness, in terms of CaCO₃ content, of 100 mg/liter, a total alkalinity, in terms of CaCO₃ content, of 100 mg/liter, a phosphate ion concentration, in terms of PO₄ ³⁻ of 6.0 mg/liter and a zinc ion concentration, in terms of Zn²⁺, of 3.5 mg/liter. The total alkalinity refers to the total acids consumption of a sample titrated by acid to a pH of 4.8 from the alkaline side.

The conical beaker was sealed with a polyethylene film, and left in a water bath filled with water having a controlled temperature of 60° C. After 40 hours, the test liquid was taken out and filtered through a filer paper having a pore diameter of 0.1 μm, and the phosphate ion concentration and the zinc ion concentration which remained in the resulting filtrate were measured to be 9.0 mg/liter in total.

Comparative Example 30:

The same experiment as in Example 16 was repeated except that a solution of the sodium salt of an isoprenesulfonic acid/acrylic acid (25/75, by mol %) binary copolymer having a weight-average molecular weight of 22,000 was used as the scaling-inhibition and fouling-prevention agent and that the concentration of the agent was 4 mg, in terms of the solid content, per liter. The sum of the phosphate ion concentration and the zinc ion concentration which remained in the filtrate was 9.0 mg/liter.

Comparative Example 31:

The same experiment as in Example 16 was repeated except that a solution of a sodium polyacrylate having a weight average molecular weight of 5,000 was used as the scaling-inhibition and fouling-prevention agent and that the concentration of the agent was 10 mg, in terms of the solid content, per liter. In this comparative example, an aqueous solution of 1 wt. %-sodium hydroxide was used for the adjustment of the pH of the mixture in the last step. The sum of the phosphate ion concentration and the zinc ion concentration which remained in the filtrate was 3.5 mg/liter.

Comparative Example 32:

The same experiment as in Example 16 was repeated except that no scaling-inhibition and fouling-prevention agent was added. In this, an aqueous solution of 1 wt. %-sodium hydroxide was used for the adjustment of the pH of the mixture in the last step. The sum of the phosphate ion concentration and the zinc ion concentration which remained in the filtrate was 0.2 mg/liter.

The results of Example 16 and Comparative Examples 30 to 32 are shown in Table 7.

                                      TABLE 7                                      __________________________________________________________________________                                         Sum of Phosphate                                                               Ion Concentration                                                              and Zinc Ion                               Scaling-inhibition           Amount Added                                                                          Concentration                              and Fouling-  IPS/AA/AMPS    (mg of solid                                                                          Remaining                                  prevention Agent                                                                             (by mol)                                                                              Molecular Weight                                                                       content/liter)                                                                        (mg/liter)                                 __________________________________________________________________________     Example 16                                                                           IPS/AA/AMPS                                                                            20/75/5                                                                               22,000  4      9.0                                              Copolymer.sup.(1)                                                        Comparative                                                                          IPS/AA  25/75/0                                                                               22,000  4      9.0                                        Example 30                                                                           Copolymer.sup.(1)                                                        Comparative                                                                          Sodium  0/100/0                                                                                5,000  10     3.5                                        Example 31                                                                           Polyacrylate                                                             Comparative                                                                          Not added.                                                                             --     --      0      0.2                                        Example 32                                                                     __________________________________________________________________________      Notes:                                                                         .sup.(1) Sodium Salt                                                           IPS: Isoprenesulfonic Acid                                                     AA: Acrylic Acid                                                               AMPS: Acrylamido2-methylpropanesulfonic Acid                             

As discussed previously, if the effectiveness is larger from the scaling-inhibition and fouling-prevention agent tested against the precipitation of zinc phosphate, the test liquid to which the agent was added will produce a smaller amount of the zinc phosphate precipitate therein. Therefore, the sum total of the phosphate ion content and the zinc ion content of the filtrate from the test liquid containing the more effective agent will be nearer to the sum total of the phosphate ion content and the zinc ion content of the original test liquid which was 9.5 mg/liter.

However, if the effectiveness is smaller from the scaling-inhibition and fouling-prevention agent tested against the precipitation of zinc phosphate, the test liquid to which the agent was added will produce a larger amount of the zinc phosphate precipitate therein. Since the precipitate is removed through the filtration of the test liquid containing the agent, the filtrate from he less effective agent will have a smaller total phosphate ion and zinc ion content.

From the results in Table 7, it can be seen that both the addition of the scaling-inhibition and fouling-prevention agent of the present invention comprising an isoprenesulfonic acid/acrylic acid/acrylamido-2-methylpropanesulfonic acid ternary copolymer to the test liquid in an amount of 4 mg, in terms of the solid content of the agent, per liter of the test liquid, and the addition of the comparative agent comprising an isoprenesulfonic acid/acrylic acid copolymer to the same test solution in the same amount resulted in the same value, 9.0 mg/liter, of the sum of the phosphate ion concentration and the zinc ion concentration which remained in the filtrate.

This demonstrates that the two agents have the same effect against the precipitation of zinc phosphate in the test liquid. However, as previously demonstrated from the results in Table 6, the effect of the scaling-inhibition and fouling-prevention agent of the present invention comprising an isoprenesulfonic acid/acrylic acid/acrylamido-2-methylpropanesulfonic acid ternary copolymer against the precipitation of calcium phosphate is higher than that of the comparative agent comprising an isoprenesulfonic acid/acrylic acid against the same.

Accordingly, it is apparent that the scaling-inhibition and fouling-prevention agent of the present invention is preferable to the comparative agent because the agent of the present invention is more broadly effectively applicable to various systems than the prior art comparison.

Regarding the other comparative agent comprising a sodium polyacrylate, even when it was added to the same test liquid in the increased amount of 10 mg, in terms of the solid content of the agent, per liter of the test liquid, the sum of the phosphate ion concentration and the zinc ion concentration which remained in the filtrate was nonetheless only 3.5 mg/liter.

Accordingly, it is apparent that the scaling-inhibition and fouling-prevention agent of the present invention is more effective and, hence, more preferable than the comparative agent comprising a sodium polyacrylate.

IID) Test for Preventing Precipitation of Iron Oxide and Iron Hydroxide

Example 17:

The components 1) demineralized water, 2) a solution of a scaling-inhibition and fouling-prevention agent comprising the sodium salt of an isoprenesulfonic acid/acrylic acid/acrylamido-2-methylpropanesulfonic acid (20/75/5, by mol %) ternary copolymer having a weight average molecular weight of 15,000, 3) a solution of the sodium hydrogencarbonate, 4) a solution of the sodium silicate No. 3, 5) a solution of calcium chloride, a solution of magnesium sulfate, and 6) a solution of ferric chloride were put into a 500-ml conical beaker in that order. Afterwards, an aqueous solution of 1 wt.% sulfuric acid was added thereto to adjust the pH of the resulting mixture.

Thus, 500 ml of a test liquid was prepared having a pH of 8.8, a solid content of the scaling-inhibition and fouling-prevention agent of 5.0 mg/liter, a calcium hardness, in terms of CaCO₃ content, of 250 mg/liter, a magnesium hardness, in terms of CaCO₃ content, of 100 mg/liter, a total alkalinity, in terms of CaCO₃ content, of 250 mg/liter, a silica content, in terms of SiO₂, of 100 mg/liter and a total iron content, in terms of Fe, of 10 mg/liter. The total alkalinity refers to the total acids consumption of a sample titrated by acid to a pH of 4.8 from the alkaline side. It is common practice in water treatment to express parameter values in terms of CaCO₃ content.

The conical beaker was sealed with a polyethylene film, and left in a water bath filled with water having a controlled temperature of 30° C., for 20 hours. After this treatment, the beaker was taken out, and the dissolved iron content of the supernatant thus separated in the beaker was measured to be 10.0 mg Fe/liter.

Example 18:

The same experiment as in Example 17 was repeated, except that a solution of the sodium salt of an isoprenesulfonic acid/acrylic acid/acrylamido-2-methylpropanesulfonic acid (20/75/5, by mol %) ternary copolymer having a weight average molecular weight of 22,000 was used as the scaling-inhibition and fouling-prevention agent at a concentration of 5.0 mg, in terms of the solid content, per liter. The dissolved iron content of the supernatant was 10.0 mg Fe/liter.

Comparative Example 33:

The same experiment as in Example 17 was repeated, except that a solution of the sodium salt of an isoprenesulfonic acid/acrylic acid (25/75, by mol %) binary copolymer having a weight average molecular weight of 16,000 was used as the scaling-inhibition and the fouling-prevention agent with a concentration of 7.5 mg, in terms of the solid content, per liter. The dissolved iron content of the supernatant was 10.0 mg Fe/liter.

Comparative Example 34:

The same experiment as in Example 17 was repeated, except that the same scaling-inhibition and fouling-prevention agent was used as that used in Comparative Example 33 at a concentration of 5.0 mg, in terms of the solid content, per liter. The dissolved iron content of the supernatant was 7.8 mg Fe/liter.

Comparative Example 35:

The same experiment as in Example 17 was repeated, except that a solution of the sodium salt of an isoprenesulfonic acid/acrylic acid (25/75, by mol %) binary copolymer having a weight average molecular weight of 22,000 was used as the scaling-inhibition and the fouling-prevention agent at a concentration of 7.5 mg, in terms of the solid content, per liter. The dissolved iron content of the supernatant was 10.0 mg Fe/liter.

Comparative Example 36:

The same experiment as in Example 17 was repeated, except that the same scaling-inhibition and fouling-prevention agent was used as that used in Comparative Example 35, at a concentration of 5.0 mg, in terms of the solid content, per liter. The dissolved iron content of the supernatant was 8.0 mg Fe/liter.

Comparative Example 37:

The same experiment as in Example 18 was repeated, except that a solution of sodium hexametaphosphate was used as the scaling-inhibition and fouling-prevention agent at a concentration of 10.0 mg, in terms of the solid content, per liter. The dissolved iron content of the supernatant was 3.3 mg Fe/liter.

Comparative Example 38:

The same experiment as in Example 17 was repeated, except that a solution of sodium hexametaphosphate was used as the scaling-inhibition and fouling-prevention agent at a concentration of 7.5 mg, in terms of the solid content, per liter. The dissolved iron content of the supernatant was 2.4 mg Fe/liter.

Comparative Example 39:

The same experiment as in Example 17 was repeated, except that a solution of a sodium polyacrylate having a weight average molecular weight of 5,000 was used as the scaling-inhibition and fouling-prevention agent at a concentration of 10.0 mg, in terms of the solid content, per liter. The dissolved iron content of the supernatant was 6.0 mg Fe/liter.

Comparative Example 40:

The same experiment as in Example 17 was repeated, except that no scaling-inhibition and fouling-prevention agent was added. The dissolved iron content of the supernatant was 0.4 mg Fe/liter.

The results of Examples 17 to 18 and Comparative Examples 33 to 40 are shown in Table 8.

                                      TABLE 8                                      __________________________________________________________________________                                              Dissolved Iron                        Scale inhibiting                  Amount Added                                                                          Concentration                         and fouling        IPS/AA/AMPS    (mg of solid                                                                          Remained                              preventing Agent   (by mol)                                                                              Molecular Weight                                                                       content/liter)                                                                        (mg Fe/liter)                         __________________________________________________________________________     Example 17                                                                           IPS/AA/AMPS  20/75/5                                                                               15,000  5.0    10.0                                        Copolymer.sup.(1)                                                        Example 18                                                                           IPS/AA/AMPS  20/75/5                                                                               22,000  5.0    10.0                                        Copolymer.sup.(1)                                                        Comparative                                                                          IPS/AA       25/75/0                                                                               16,000  7.5    10.0                                  Example 33                                                                           Copolymer.sup.(1)                                                        Comparative                                                                          IPS/AA       25/75/0                                                                               16,000  5.0    7.8                                   Example 34                                                                           Copolymer.sup.(1)                                                        Comparative                                                                          IPS/AA       25/75/0                                                                               22,000  7.5    10.0                                  Example 35                                                                           Copolymer.sup.(1)                                                        Comparative                                                                          IPS/AA       25/75/0                                                                               22,000  5.0    8.0                                   Example 36                                                                           Copolymer.sup.(1)                                                        Comparative                                                                          Sodium Hexametaphosphate                                                                    --     --      10.0   3.3                                   Example 37                                                                     Comparative                                                                          Sodium Hexametaphosphate                                                                    --     --      7.5    2.4                                   Example 38                                                                     Comparative                                                                          Sodium Polyacrylate                                                                         0/100/0                                                                                5,000  10.0   6.0                                   Example 39                                                                     Comparative                                                                          Not Added.   --     --      0      0.4                                   Example 40                                                                     __________________________________________________________________________      Notes:                                                                         .sup.(1) Sodium Salt                                                           IPS: Isoprenesulfonic Acid                                                     AA: Acrylic Acid                                                               AMPS: Acrylamido2-methylpropanesulfonic Acid                             

As discussed previously, if no scaling-inhibition and fouling-prevention agent is added to the test liquid or if the scaling-inhibition and fouling-prevention agent added is ineffective, the iron component in the above test liquid would precipitate out in the form of iron oxide hydrate or iron hydroxide. Therefore, the effect can be evaluated, of the scaling-inhibition and fouling-prevention agents as added to the test liquid, with respect to the agents' effectiveness at dispersing the iron oxide or iron hydroxide precipitate potentially formed in the test liquid. The dispersing power of the agents is correlated to the amount of iron, unprecipitated, remaining in the test liquid.

Thus, measuring the dissolved iron content of the supernatant separated from the test liquid to which the agent was added indicates how effective the agent was at inhibiting the formation of iron based scaling. Accordingly, the higher the iron concentration remaining in the supernatant, the more effective the scaling-inhibition and fouling-prevention agent.

The scaling-inhibition and fouling-prevention agent of the present invention comprising an isoprenesulfonic acid/acrylic acid/acrylamido-2-methylpropanesulfonic acid copolymer, when added to the test liquid in an amount of 5 mg in terms of the solid content thereof, per liter, inhibited the precipitation of iron of up to a measured 10 mg/liter of iron in the supernatant, while acting to completely disperse and keep the iron in solution in the test liquid.

In comparison, however, when the comparative agent comprising an isoprenesulfonic acid/acrylic acid binary copolymer was added to the same test liquid in an amount of 5 mg, in terms of the solid content thereof, per liter, it could not inhibit the precipitation of iron to 10 mg/liter in the supernatant. In order to inhibit the precipitation of iron to a concentration as high as 10 mg/liter in the test liquid, it was necessary to increase the agent amount to 7.5 mg/liter, in terms of the solid content, of the comparative agent to the test liquid. Thus, it is clear from the data that the ternary copolymer of present invention was more effective at inhibiting iron precipitation than the binary copolymer of the prior art.

Regarding the other comparative agents comprising sodium hexametaphosphate or sodium polyacrylate of the prior art, the concentration of iron in the supernatant did not reach 10 mg/liter even when the agents were added to the test liquid in an amount of 10 mg, in terms of the solid content, per liter. Thus, it is clear from the data that the scaling-inhibition and fouling-prevention agent of the present invention is much more effective for dispersing iron oxide and iron hydroxide in water than the comparative agents comprising sodium hexametaphosphate or sodium polyacrylate.

IIIA) Scaling and Corrosion Tests in Pilot Plant of Open Recirculating, Cooling water System (.Cooling Tower)--Part 1

Examples 19 and 20, Comparative Example 41:

Using a pilot plant as shown in FIG. 1, the water-treating agent of the present invention was tested with respect to its effect against scaling and corrosion therein. The test period was 23 days.

The water balance in the cooling system is shown in Table 9. The quality of make up water as supplied to the system and that of the cooling water as circulating therein are shown in Table 10. The operational conditions for the heat exchangers 1, 2, 3, and 4 used herein are shown in Table 11. The chemicals used herein and their concentrations are shown in Table 12.

                  TABLE 9                                                          ______________________________________                                         Water Balance in Cooling System                                                ______________________________________                                         Amount of Cooling Water (liter/hr)                                                                     810                                                    Evaporation Loss (liter/hr)                                                                             6                                                     Total Amount of Blowdown Water (liter/hr)                                                              1.5                                                    Amount of Make-up Water (liter/hr)                                                                     7.5                                                    Cycles of Concentration.sup.( *.sup.1)                                                                 5.0                                                    Supply Water Temperature (°C.)                                                                  40                                                     Return Water Temperature (°C.)                                                                  47                                                     Holding Water Volume (liter)                                                                           95                                                     Retention Time.sup.(*2) (hr)                                                                           63                                                     ______________________________________                                          .sup.(*.sup.1) Cycles of Concentration = (amount of makeup water,              liter/hr)/(amount of total blowdown, liter/hr)                                 .sup.(*.sup.2) Retention Time (hr) = (holding water volume of system,          liter)/(amount of total blowdown, liter/hr)                              

                  TABLE 10                                                         ______________________________________                                         Quality of Make-up Water and Quality of Cooling Water                                           Make-up water                                                                           Cooling Water                                        ______________________________________                                         pH                 7.5-7.9    8.9-9.2                                          Electrical conductivity (μS/cm)                                                                297-352    1,483-1,760                                      Total Hardness (mg CaCO.sub.3 /liter)                                                              91-120    455-598                                          Calcium Hardness (mg CaCO.sub.3 /liter)                                                           70-92      350-460                                          Magnesium Hardness (mg CaCO.sub.3 /liter)                                                         21-28      105-138                                          total alkalinity (mg CaCO.sub.3 /liter)                                                           75-80      375-400                                          Chloride Ion (mg/liter)                                                                           38-46      190-230                                          Sulfate Ion (mg/liter)                                                                            16-22       80-110                                          Silica (mg SiO.sub.2 /liter                                                                       29-37      146-184                                          ______________________________________                                    

                  TABLE 11                                                         ______________________________________                                         Operational Conditions of Heat Exchangers                                      ______________________________________                                         Temperature of                                                                          Inlet of Heat Exchanger Part No. 1 (H/E                                                              40                                              Water (°C.)                                                                      1)                                                                             Outlet of Heat Exchanger Part No. 4 (H/E                                                             47                                                       4)                                                                    Skin Temperature of Heat Exchanger Tube (at outlet of H/E                                                 70                                                  4) (°C.)                                                                Water Flow Velocity in Heat Exchanger (m/s)                                                               0.6                                                 Heat Flux (kcal/m.sup.2 /h)                                                                               39,000                                              Material of Heat Exchanger Tubes                                                                          Carbon Steel                                        ______________________________________                                    

                  TABLE 12                                                         ______________________________________                                         Chemicals Used                                                                                                Comparative                                                  Example 19                                                                             Example 20                                                                               Example 41                                      ______________________________________                                         Corrosion                                                                              HEDP.sup.( *.sup.3)                                                                       4.0       4.0     4.0                                       Inhibitor                                                                              BT.sup.( *.sup.4)                                                                         0.5       0.5     0.5                                       (mg/liter)                                                                     Scaling-                                                                               IPS/AA/    11.0      --      --                                        inhibition                                                                             AMPS.sup.( *.sup.5)                                                    Agent (mg                                                                              IPS/AA/    --        11.0    --                                        solid/-liter)                                                                          HEMA.sup.( *.sup.6)                                                            IPS/AA.sup.( *.sup.7)                                                                     --        --      11.0                                      ______________________________________                                          .sup.(*.sup.3) 2hydroxyethylidene-diphosphonic Acid                            .sup.(*.sup.4) Benzotriazole                                                   .sup.(*.sup.5) Isoprenesulfonic acid (IPS)/Acrylic acid                        (AA)/Acrylamido2-methylpropanesulfonic acid (AMPS) ternary copolymer           having a molar ratio, IPS/AA/AMPS of 15/75/10 and a molecular weight of        15,000                                                                         .sup.(*.sup.6) IPS/AA/2Hydroxyethyl methacrylate (HEMA) ternary copolymer      having a molar ratio, IPS/AA/HEMA of 20/70/10 and a molecular weight of        13,000                                                                         .sup.(*.sup.7) IPS/AA binary copolymer having a molar ratio, IPS/AA of         25/75 and a molecular weight of 16,000                                   

The corrosion rate of the test electrodes as installed at the inlet of the heat exchanger No. 1 (H/E 1) and at the outlet of the heat exchanger No. 4 (H/E 4) was measured, using a corrosion monitor (Corrosion Monitor 500C Model, produced by Toho Giken KK) in accordance with a linear polarization method. The results obtained are shown in Table 13. The scaling rate on the heat transfer tube of each heat exchanger was measured and shown in Table 14.

                  TABLE 13                                                         ______________________________________                                         Results of Corrosion Test                                                                     Rate of Corrosion (mg/dm.sup.2 /day)                            Installation of                                                                           Material of                                                                              Example  Example                                                                               Comparative                               Electrode  Electrode 19       20     Example 41                                ______________________________________                                         Inlet of H/E 1 (tem-                                                                      Carbon Steel                                                                             5.5      4.0    6.4                                       perature of water:                                                                        Copper    0.5      0.5    0.8                                       40° C.)                                                                 Outlet of H/E 4                                                                           Carbon Steel                                                                             7.4      6.3    10.1                                      temperature of                                                                            Copper    0.8      0.4    1.2                                       water: 47° C.)                                                          ______________________________________                                    

                  TABLE 14                                                         ______________________________________                                         Results of Scaling Test                                                                     Scaling Rate (mg/cm.sup.2 /month)                                                                    Comparative                                 Heat Exchanger Example 19                                                                               Example 20                                                                               Example 41                                  ______________________________________                                         H/E 1 (temperature of water at                                                                0.9       1.1       3.4                                         inlet: 40° C.)                                                          H/E 2          0.9       1.1       3.5                                         H/E 3          2.0       1.0       8.9                                         H/E 4 (temperature of water at                                                                2.6       1.8       12.7                                        outlet: 47° C.)                                                         ______________________________________                                    

As is obvious from the test results displayed above, the compositions of the present invention of Examples 19 and 20 are superior to the comparative composition of Comparative Example 41 by being more effective than Comparative Example 41 against the corrosion of carbon steel and copper and against the scaling of heat transfer tubes in the heat exchangers.

Examination of the scale formed in the above experiment found that the scale from Comparative Example 41 consisted of 65% magnesium silicate, while the magnesium silicate content of the scale formed in Example 19 was 35% and that of the scale formed in Example 20 was 25%. It is apparent from these results that the compositions of the present invention are very effective against the formation of silica scale, more so than that of the comparative composition.

Accordingly, it is seen from the above data that the scaling-inhibition and fouling-prevention agent of the present invention, which is obtained by introducing a third component of acrylamido-2-methylpropanesulfonic acid and/or 2-hydroxyethyl methacrylate into an isoprenesulfonic acid-acrylic acid binary copolymer system, exhibits a greater effectiveness against corrosion and scaling in water systems than an isoprenesulfonic acid-acrylic acid binary copolymer, when combined with a corrosion inhibitor.

IIIB) Scaling and Corrosion Tests in the Pilot Plant of Open Recirculating, Cooling-water System (Cooling Tower)--Part 2

Example 21, Comparative Example 42:

Using the same pilot plant under the same operational conditions as in Examples 19 and 20 but varying the quality of water supplied into the plant, the water-treating agent of the present invention was tested with respect to the agent's effectiveness against scaling and corrosion therein. The test period was 23 days. The water balance in the cooling system was the same as that in Table 9. The operational conditions employed herein for the heat exchanger were the same as those in Table 11.

The quality of water as supplied to the system and that of the cooling water as circulating therein are shown in Table 15. The chemicals used herein and their concentrations are shown in Table 16.

                  TABLE 15                                                         ______________________________________                                         Quality of Make-up Water and Quality of Cooling Water                                           Make-up water                                                                           Cooling Water                                        ______________________________________                                         pH                 7.3-7.6    8.3-8.7                                          Electrical conductivity (μS/cm)                                                                172-192      810-1,016                                      Total Hardness (mg CaCO.sub.3 /liter)                                                             42-58      196-305                                          Calcium Hardness (mg CaCO.sub.3 /liter)                                                           35-46      163-245                                          Magnesium Hardness (mg CaCO.sub.3 /liter)                                                          7-12      33-60                                            total alkalinity (mg CaCO.sub.3 /liter)                                                           37-41      158-215                                          Chloride Ion (mg/liter)                                                                           29-32      134-167                                          Sulfato Ion (mg/liter)                                                                            17-19      74-95                                            Silica (mg SiO.sub.2 /liter)                                                                       9-11      40-60                                            ______________________________________                                    

                  TABLE 16                                                         ______________________________________                                         Chemicals Used                                                                               Example 21                                                                             Comparative Example 42                                   ______________________________________                                         Corrosion SHP.sup.( *.sup.8)                                                                       3.0       3.0                                              Inhibitor NaH.sub.2 PO.sub.4                                                                       1.5       1.5                                              (mg/liter)                                                                               PBTC.sup.( *.sup.9)                                                                      3.0       3.0                                                        ZnCl.sub.2                                                                               6.0       6.0                                                        TT.sup.( *.sup.10)                                                                       0.5       0.5                                              Scaling-  IPS/AA/   12.0      --                                               Inhibition Agent                                                                         HEMA.sup.( *.sup.11)                                                 (mg solid/-liter)                                                                        IPS/AA.sup.( *.sup.12)                                                                   --        12.0                                             ______________________________________                                          .sup.(*.sup.8) Sodium Hexametaphosphate                                        .sup.(*.sup.9) Phosphonobutanetricarboxylic Acid                               .sup.(*.sup.10) Tolyltriazole                                                  .sup.(*.sup.11) Same as (*6) in Table 12                                       .sup.(*.sup.12) Same as (*7) in Table 12                                 

In the same manner as in Example 19, the corrosion rate of the test electrodes and the scaling rate of the heat-transfer tubes were measured. The data obtained are shown in Tables 17 and 18.

                  TABLE 17                                                         ______________________________________                                         Results of Corrosion Test                                                                              Corrosion Rate (mg/dm.sup.2 /day)                      Installation  Material of          Comparative                                 of Electrode  Electrode Example 21 Example 42                                  ______________________________________                                         Inlet of H/E 1                                                                               Carbon Steel                                                                             1.6        5.8                                         (temperature of water:                                                                       Copper    0.3        0.4                                         40° C.)                                                                 Outlet of H/E 4 (tempera-                                                                    Carbon Steel                                                                             1.7        7.2                                         ture of water: 47° C.)                                                                Copper    0.2        0.5                                         ______________________________________                                    

                  TABLE 18                                                         ______________________________________                                         Results of Scaling Test                                                                          Scaling Rate (mg/cm.sup.2 /month)                                                         Comparative                                       Heat Exchanger    Example 21 Example 42                                        ______________________________________                                         H/E 1 (temperature of water at                                                                   1.0        3.5                                               inlet: 40° C.)                                                          H/E 2             1.0        3.3                                               H/E 3             1.1        7.2                                               H/E 4 (temperature of water at                                                                   1.5        8.1                                               outlet: 47° C.)                                                         ______________________________________                                    

As in Examples 19 and 20, the scaling-inhibition and fouling-prevention agent of the present invention exhibited a greater effectiveness against corrosion and scaling in the water system tested herein, than the comparative, isoprenesulfonic acid-acrylic acid copolymer, when combined with a corrosion inhibitor.

As has been described in detail and demonstrated by the data hereinabove, the water-treating agent of the present invention, comprising a conjugated dienesulfonic acid/(meth)acrylic acid/2-hydroxyethyl (meth)acrylate ternary copolymer or comprising a conjugated dienesulfonic acid/(meth)acrylic acid/(meth)acrylamido-2-methylalkanesulfonic acid ternary copolymer, exhibits an excellent anti-scaling and anti-fouling effect in water systems and can therefore prevent water systems from malfunctions arising from reduced thermal efficiency and reduced water flow rate caused by the adhesion or deposition of scale, sludge and slime onto heat exchangers, heat transfer heating pipes, and other such pipe lines that constitute water systems.

Having described preferred embodiments of the invention with reference to the accompanying drawing, it is to be understood that the invention is not limited to those precise embodiments, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of the invention as defined in the appended claims.

Although only a single or few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiment(s) without materially departing from the novel teachings and advantages of this invention.

Accordingly, all such modifications are intended to be included within the scope of this invention as defined in the following claims, In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures. Thus, although a nail and screw may not be structural equivalents in that a nail relies entirely on friction between a wooden part and a cylindrical surface whereas a screw's helical surface positively engages the wooden part in the environment of fastening wooden parts, a nail and a screw may be equivalent structures. 

What is claimed is:
 1. A method for treating water to prevent scale and slime formation and to prevent fouling, comprising the steps of:polymerizing a combination comprisingA) a first monomer selected from the group consisting of a conjugated dienesulfonic acid and a salt of a conjugated dienesulfonic acid, said conjugated dienesulfonic acid represented by the general formula 1!: ##STR22## wherein R¹, R², R³, R⁴, R⁵ and R⁶ each represents a member selected from the group consisting of a hydrogen atom, a methyl substituent, and a --SO₃ X¹ substituent, wherein at least one of R¹ to R⁶ is a methyl substituent, wherein at least one of R¹ to R⁶ is a --SO₃ X¹ substituent, and wherein X¹ represents a member selected from the group consisting of hydrogen atom, a monovalent metal, an ammonium substituent, and an ammonium substituent which is mono substituted by an organic substituent; B) a second monomer selected from the group consisting of a (meth)acrylic acid and a salt of a (meth)acrylic acid, said (meth)acrylic acid represented by the general formula 2!: ##STR23## wherein R⁷ represents a hydrogen atom or a methyl substituent; and X² represents a member selected from the group consisting of a hydrogen atom, a monovalent metal, an ammonium substituent, and an ammonium substituent which is mono substituted by an organic substituent; and C) a third monomer selected from the group consisting of a 2-hydroxyethyl (meth)acrylate represented by the general formula 3!, a (meth)acrylamido-2-methylalkanesulfonic acid, and a salt of a (meth)acrylamido-2-methylalkanesulfonic acid, said (meth)acrylamido-2-methylalkanesulfonic acid represented by the general formula 4!: ##STR24## wherein R⁸ represents a hydrogen atom or a methyl substituent, ##STR25## wherein R⁹ and R¹⁰ are members selected from the group consisting of a hydrogen atom and a methyl substituent; and X³ represents a member selected from the group consisting of a hydrogen atom, a monovalent metal, an ammonium substituent, and an ammonium substituent which is mono substituted by an organic substituent,to form a ternary copolymer having a weight average molecular weight of at least about 14,000, wherein said step of polymerizing includes polymerizing said combination of from about 5 to about 50 mol % of said first monomer, from about 40 to about 90 mol % of said second monomer, and from about 1 to about 20 mol % of said third monomer; and adding said ternary copolymer to a water system in an amount of from about 0.1 to about 1000 mg/liter.
 2. The method for treating water as claimed in claim 1, wherein said third monomer is 2-hydroxyethyl (meth)acrylate.
 3. The method for treating water as claimed in claim 1, wherein said third monomer is a member selected from the group consisting of said (meth)acrylamido-2-methylalkanesulfonic acid and said salt of said (meth)acrylamido-2-methylalkanesulfonic acid.
 4. The method for treating water as claimed in claim 1, wherein said step of polymerizing includes forming said ternary copolymer having a weight average molecular weight of from about 14,000 to about 300,000.
 5. The method for treating water as claimed in claim 1, wherein said step of polymerizing includes polymerizing wherein at least one of said X¹, said X², and said X³ is formed through the reaction of --SO₃ H or --COOH with a primary amine selected from the group consisting of methylamine, ethylamine, propylamine, isopropylamine, butylamine, isobutylamine, sec-butylamine, tert-butylamine, pentylamine, hexylamine, cyclohexylamine, benzylamine, and monoethanolamine to produce said ammonium substituent mono substituted by an organic group.
 6. The method for treating water as claimed in claim 1, further including a step of adding a corrosion inhibitor to the water system.
 7. The method for treating water as claimed in claim 6, wherein said step of adding a corrosion inhibitor includes adding a member selected from the group consisting of polyvalent metal salts, phosphonates, azoles, phosphates, polyphosphates, phosphonocarboxylates, amines and phosphoric esters.
 8. The method for treating water as claimed in claim 6, wherein said step of adding a corrosion inhibitor includes adding said corrosion inhibitor in an amount of from about 0.1 to about 10 parts by weight relative to one part of said ternary copolymer. 